1. Consider the following pairs:
Commonly used material vs. Unwanted or controversial chemicals found in them
1. Lipstick: Lead
2. Soft drinks: Brominated vegetable oils
3. Chinese fast food: Monosodium glutamate Which of the pairs given above is/are correctly matched?
(a) 1 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
Ans. (d) Mono sodium Glutamate (MSG) is a flavor enhancer in Chinese food, but leads to obesity and liver inflation. This was in news because of Maggie noodles controvery. So, 3 is right. • Brominated vegetable oils are used as stabilizers in the baked goods, soft drinks, soups, jellies etc. but banned in UK after 1970. so, 2 is right. There is only one combination where 1 and 3 are together i.e. answer “D”: 1, 2 and 3 are correct.
UPSC Previous Year Paper [2017]
2. Which of the following is/are the example/examples of chemical change?
1. Crystallization of sodium chloride
2. Melting of ice
3. Souring of milk
Select the correct answer using the code given below.
(a) 1 and 2 only
(b) 3 only
(c) 1, 2 and 3
(d) None
Ans. (b) Melting of ice is not a chemical change. It is a physical change from one state to another state. It does not produce anything new. Similarly, crystallization of sodium chloride is also not an example of chemical change. Souring of milk is a chemical change because once milk is soured, it produces product with different chemical properties. Hence, (b) is the correct answer.
UPSC Previous Year Paper [2014]
3. Which one of the following sets of elements was primarily responsible for the origin of life on the Earth?
(a) Hydrogen, Oxygen, Sodium
(b) Carbon, Hydrogen, Nitrogen
(c) Oxygen, Calcium, Phosphorous
(d) Carbon, Hydrogen, Potassium
Ans. (b) Carbon, Hydrogen and Nitrogen gases were primarily responsible for origin of life on the earth.
UPSC Previous Year Paper [2012]
4. The increasing amount of carbon dioxide in the air is slowly raising the temperature of the atmosphere, because it absorbs
(a) the water vapour of the air and retains its heat
(b) the UV part of the solar radiation
(c) all the solar radiations
(d) the infrared part of the solar radiation
Ans. (d) Effects of Increasing Carbon di oxides: Land plants and the ocean usually take up about 55 percent of the extra carbon people have put into the atmosphere while about 45 percent has remain in the atmosphere. Eventually, the land and oceans will take up most of the extra carbon dioxide, but as much as 20 percent may remain in the atmosphere for many thousands of years. The changes in the carbon cycle impact each reservoir. Excess carbon in the atmosphere warms the planet and helps plants on land grow more. Excess carbon in the ocean makes the water more acidic, putting marine life in danger.
UPSC Previous Year Paper [2012]
5. Lead, ingested or inhaled, is a health hazard. After the addition of lead to petrol has been banned, what still are the sources of lead poisoning?
1. Smelting units
2. Pens and pencils
3. Paints
4. Hair oils and cosmetics
Select the correct answer using the codes given below:
(a) 1, 2 and 3 only
(b) 1 and 3 only
(c) 2 and 4 only
(d) 1, 2 ,3 and 4
Ans. (a) Pens and pencils are commonly used by children. Since we all know that lead is a significant health hazard and poses grave threats to human health, logic dictates that it must not be used in pen pencils and toys, which are used by children. Young children are particularly vulnerable because they absorb 4–5 times as much ingested lead as adults from a given source. Moreover, children’s innate curiosity and their age-appropriate hand-to-mouth behaviour result in their mouthing and swallowing leadcontaining or lead-coated objects, such as contaminated soil or dust and flakes of decaying leadcontaining painence, the correct option must be B.
UPSC Previous Year Paper [2012]
6. A company marketing food products advertises that its items do not contain trans-fats. What does this campaign signify to the customers?
1. The food products are not made out of hydrogenated oils.
2. The food products are not made out of animal fats/ oils.
3. The oils used are not likely to damage the cardiovascular health of the consumers.
Which of the statements given above is/are correct?
(a) 1 only. (b) 2 and 3 only.
(c) 1 and 3 only. (d) 1,2 and 3.
Ans. (c) Trans fats are hydrogenated oil and not made from animal or vegetable oils and therefore, any campaigns against trans fats must not say that it is not made out of animal fats/oils. Hence, C is the correct answer.
UPSC Previous Year Paper [2011]
7. Consider the following:
1. Oxides of Hydrogen
2. Oxides of Nitrogen
3. Oxides of Sulphur
Which of the above causes/cause acid rain?
(a) 1 and 2 only
(b) 3 only
(c) 2 and 3 only
(d) 1, 2 and 3
Ans. (c) Acid rain is formed by a chemcial reaction that begins when compounds like sulphur dioxide and nitrogen oxides released into the air. These react with water, oxygen, and other chemicals to form more acidic pollutants known as acid rain.
UPSC Previous Year Paper [2010]
8. Chlorination is a process used for water purification. The disinfecting action of chlorine is mainly due to
(a) The formation of hydrochloric acid when chlorine is added to water
(b) The formation of hypochlorous acid when chlorine is added to water
(c) The formation of nascent oxygen when chlorine is added to water
(d) The formation of hydrogen when chlorine is added to water
Ans. (c) Water chlorination is the process of adding chlorine or hypochlorite to water this method is used to kill certain bacteria and other microbes as chlorine is highly toxic.
UPSC Previous Year Paper [2010]
9. Excessive release of the pollutant carbon monoxide (CO) into the air may produce a condition in which oxygen supply to the human body decreases. What causes this condition?
(a) When inhaled into the human body, CO is converted into CO2
(b) The inhaled CO has much higher affinity for haemoglobin as compared to oxygen
(c) The inhaled CO destroys the chemical Structure of haemoglobin
(d) The inhaled CO adversely affects the respiratory centre in the brain
Ans. (b) Carbon monoxide poisoning is the most common type of fatal air poisoning in many countries. Carbon monoxide is colorless, odosless and tasteless, but highly toxic. It combines with hemoglobin to produce carboxyhemoglobin, which usuers the space in hamoglobin that normally carries oxygen, but is ineffective for delivering oxygen to bodily tissues.
UPSC Previous Year Paper [2010]
10. In a dry cell (battery), which of the following are used as electrolytes?
(a) Ammonium chloride and Zinc chloride
(b) Sodium chloride and Calcium chloride
(c) Magnesium chloride and Zinc chloride
(d) Ammonium chloride and calcium chloride
Ans. (a) A standard dry cell comprises a zinc annode, usually in the form of cylindrical pot, with carbon cathode in the from of central rod. The electrolyte is ammonium chloride in the form of a paste next to zinc anode.
UPSC Previous Year Paper [2009]
11. Which one of the following is used as an explosive?
(a) Phosphorus trichloride
(b) Mercuric oxide (c) Graphite
(d) Nitroglycerine
Ans. (d) Nitroglycerine is a highly explosive nature liquid that is being used in explosive industry to make various types of explosives: Nitroglycerine and its properties: Nitroglycerine is an explosive liquid which was first made by Ascanio Sobrero in 1846 by treating glycerol with a mixture of nitric and sulphuric acid. The reaction which follows is highly exothermic, i.e. it generates heat and will result in an explosion of nitroglycerine, unless the mixture is cooled while the reaction is taking place.
UPSC Previous Year Paper [2009]
12. Which one of the following pairs of metals constitutes the lightest metal and the heaviest metal, respectively?
(a) Lithium and mercury
(b) Lithium and osmium
(c) Aluminium and osmimum
(d) Aluminium and mercury
Ans. (b) Under standard conditions, Lithium is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly reactive and flammable.
UPSC Previous Year Paper [2008]
13. Which one of the following is also called Strange Gas?
(a) Argon (b) Neon
(c) Xenon (d) Nitrous oxide
Ans. (c) Xenon is called the ‘stranger or strange’ gas. This gas is very un-reactive and heavier than air, that why it is named strange (in greek it means ‘xenon’). It’s may be because of its ability to react with oxygen and fluorine form its oxides and fluorides. Symbol: Xe Atomic number: 54 Discovered by : Sir William Ramsay and Morris Travers in the Year 1898.
UPSC Previous Year Paper [2008]
14. Mixture of which one of the following pairs of gases is the cause of occurrence of most of the explosions in mines?
(a) Hydrogen and oxygen
(b) Oxygen and acetylene
(c) Methane and air
(d) Carbon dioxide and methane
Ans. (c) Methane explosions occur in mines when a buildup of methane gas, a byproduct of coal, comes into contact with a heat source in absence of sufficient air. Why coal mines explodes? There are two main types of coal mine explosionsmethane explosions and coal dust explosions. Methane explosions occur in mines when a buildup of methane gas, a byproduct of coal, comes into contact with a heat source, and there is not enough air to dilute the gas to levels below its explosion point.
UPSC Previous Year Paper [2008]
15. What is Bisphenol A (BPA)?
(a) A Medical test for detecting cancer
(b) A test for testing the use of drugs to improve performance by athletes
(c) A chemical used for the development of foodpackaging materials
(d) a special type of alloy steel [(CH3)2C(C6H4OH)2]
Ans. (c) Bisphenol A is an organic synthetic compound with the chemical formula (CH3)2C(C6H4OH)2 belonging to the group of diphenylmethane derivatives and bisphenols, with two hydroxyphenyl groups used for the development of food-packaging materials.
UPSC Previous Year Paper [2008]
16. What are Rubies and Sapphires chemically known as?
(a) Silicon dioxide (b) Aluminum oxide
(c) Lead tetraoxide (d) Boron nitride
Ans. (b) A ruby is a pink to blood-red colored gemstone, a variety of the mineral corundum (aluminium oxide). The red color is caused mainly by the presence of the element chromium. Its name comes from ruber, Latin for red. Other varieties of gem-quality corundum are called sapphires.
UPSC Previous Year Paper [2008]
17. Which one of the following does not contain silver?
(a) Horn Silver (b) German silver
(c) Ruby silver (d) Lunar caustic
Ans. (b) German Silver or Nickel Silver is a metal alloy of copper with nickel and often but not always zinc. It is named for its silvery appearance, but contains no elemental silver.
UPSC Previous Year Paper [2007]
18. Which one among the following is called philosopher’s wool?
(a) Zinc bromide (b) Zinc nitrate
(c) Zinc oxide (d) Zinc chloride
Ans. (c) Zinc Oxide is called philosopher’s wool. Thus, C is the correct answer. One of the oldest uses of zinc oxide was in alchemy. When ZnO is produced in this way, the white powder forms in very loose, airy clumps which could, with a bit of imagination, be called wooly. Hence,philosopher’s wool.
UPSC Previous Year Paper [2007]
19. Which one of the following non-metals is not a poor conductor of electricity?
(a) Sulphur
(b) Selenium
(c) Bromine
(d) Phosphorus
Ans. (b) Selenium is a chemical element with symbol Se and atomic number 34. It is a nonmetal with properties that are intermediate between the elements above and below in the periodic table, sulfur and tellurium. It rarely occurs in its elemental state or as pure ore compounds in the Earth’s crust. Due to its good conductivity of electricity, Selenium is used in solar cells.
UPSC Previous Year Paper [2007]
20. Which one of the following types of glass can cut off ultraviolet rays?
(a) Soda glass (b) Pyrex glass
(c) Jena glass (d) Crookes glass
Ans. (d) Crookes glass or Crown glass is a type of optical glass used in lenses and other optical components. It has relatively low refractive index (˜1.52) and low dispersion.
UPSC Previous Year Paper [2007]
21. Which one of the following is another name of RDX?
(a) Cyanohydrin (b) Selenium
(c) Cyclohexane (d) Cyclonite
Ans. (d) RDX is also known, but less commonly, as cyclonite, hexogen (particularly in Russian, German and German-influenced languages), T4 and chemically as cyclotrimethylenetrinitramine. Hence, D is the correct answer.
UPSC Previous Year Paper [2007]
22. Which are the materials generally employed as solder in soldering operation?
(a) Iron and tin (b) Lead and tin
(c) Aluminum and lead (d) Aluminum and iron
Ans. (b) Soldering is a process in which two or more items, usually metals, are joined together by melting and putting a filler metal (solder) into the joint, the filler metal having a lower melting point than the adjoining metal. Soldering differs from welding in that soldering does not involve melting the work pieces. In the past, nearly all solders contained lead, but environmental and health concerns have increasingly dictated use of lead-free alloys for electronics and plumbing purposes. Some examples of soft-solder are tin-lead for general purposes, tin-zinc for joining aluminium, lead-silver for strength at higher than room temperature, cadmium-silver for strength at high temperatures, zinc-aluminium for aluminium and corrosion resistance, and tin-silver and tin-bismuth for electronics.
UPSC Previous Year Paper [2006]
23. Consider the following chemicals:
(1) Benzene (2) Carbon tetrachloride
(3) Sodium Carbonate (4) Trichloroethylene
Which of the above is/are used as dry cleaning chemicals?
(a) 1 Only (b) 2 Only
(c) 1, 2 and 4 Only (d) 1, 2, 3 and 4
Ans. (c) Dry cleaning is any cleaning process for clothing and textiles using a chemical solvent other than water. The solvent used are typically toxic trichloroethylene and other hydrocarbons. Sodium Carbonate is not used as cleaning agent.
UPSC Previous Year Paper [2006]
24. Consider the following statements:
(1) Anhydrous sodium carbonate is commonly known as baking soda
(2) Baking soda is used in fire extinguishers
(3) Bleaching powder is manufactured in Hasenclever plant
Which of the statements given above is/are correct?
(a) 1, 2 and 3 (b) 2 and 3
(c) 3 only (d) 1 and 2
Ans. (c) Anhydrous sodium carbonate is the waterless crystalline form of sodium carbonate, the sodium salt of carbonic acid. Its chemical formula is Na2CO3. 10H2O and it is commonly known as washing soda. Though Baking soda is an excellent fire extinguisher but it is not used in conventional fire extinguisher due to storage and logistical problems. Baking soda thrown on a fire creates carbon dioxide and puts out the fire. This is safer than throwing water on a grease fire, which can splatter and spread the flames to flammable items. Bleaching powder is very useful chemical compound which is used extensively for bleaching of fabrics. It chemical formula is CaOCl2 and its chemical name is calcium oxychloride. Bleaching powder is manufactured in Hasenclever plant.
UPSC Previous Year Paper [2005]
25. Which one of the following is the correct sequence of the given substances in the decreasing order of their densities?
(a) Steel > Mercury > Gold
(b) Gold > Mercury > Steel
(c) Steel > Gold > Mercury
(d) Gold > Steel > mercury
Ans. (b) Among given substances, Gold has the highest density with 19.3g/cm3. Mercury stands at second place with 13.5g/mL. Steel only has density of 7.82 g/cm3.
UPSC Previous Year Paper [2005]
26. Assertion (A): The main constituent of the Liquefied Petroleum Gas is methane.
Reason(R): Methane can be used directly for burning in homes and factories where it can be supplied through pipelines. (a) Both A and R are individually true and R is the correct explanation of A
(b) Both A and R are individually true but R is not the correct explanation of A
(c) A is true but R is false
(d) A is false but R is true
Ans. (d) Liquid Petroleum Gas (LPG) mainly constitute of mixture of isopropane and butane and NOT methane. LPG has a very wide variety of uses, mainly used for cylinders across many different markets as an efficient fuel container in the agricultural, recreation, hospitality, calefaction, construction, sailing and fishing sectors. It can serve as fuel for cooking, central heating and to water heating and is a particularly cost-effective and efficient way to heat off-grid homes. In the safety font LPG cylinders must be updated to new standards in safety and user experience, giving a huge contribution for domestic usage. Thus, assertion is correct whereas reason is incorrect.
UPSC Previous Year Paper [2005]
27. Consider the following statements:
1. Baking soda is used in fire extinguishers.
2. Quicklime is used in the manufacture of glass.
3. Gypsum is used in the manufacture of Plaster of Paris.
Which of the statements given above is/are correct?
(a) 1 and 2 (b) 2 and 3
(c) 1 only (d) 1, 2 and 3
Ans. (b) Though Baking soda is one of the significant fire extinguisher agents in small scale only, it is not used in conventional fire extinguisher due to logistical and usage problems. Quicklime is used in glass production as a flux for modifying viscosity. Quicklime increases the final product durability and chemical wear resistance. Gypsum is an essential constituent of Plaster of Paris manufacturing process.
UPSC Previous Year Paper [2004]
28. Match List-I (Fuel Gases) with List-II (Major Constituents) and select the correct answer using the codes given below the Lists:
List-I : List-II
(Fuel Gases) : (Major Constituents)
A. CNG : 1. Carbon monoxide, Hydrogen
B. Coal gas : 2. Butane, Propane
C. LPG : 3. Methane, Ethane
D. Water gas : 4. Hydrogen, Methane, Carbon monoxide
Codes:
A B C D
(a) 2 1 3 4 (b) 3 4 2 1
(c) 2 4 3 1 (d) 3 1 2 4
Ans. (b) Water gas is a fuel gas consisting mainly of carbon monoxide and hydrogen, made by passing steam over incandescent coke. CNG is made by compressing natural gas, which is mainly composed of methane and ethane, to less than 1 percent of the volume it occupies at standard atmospheric pressure. Coal gas a mixture of gases chiefly hydrogen, methane, and carbon monoxide that is obtained by the destructive distillation of coal and formerly used for lighting and heating. Liquefied petroleum gas or liquid petroleum gas (LPG or LP gas), also referred to as simply propane or butane, are flammable mixtures of hydrocarbon gases used as fuel in heating appliances, cooking equipment, and vehicles.
UPSC Previous Year Paper [2004]
29. Salts of which of the following elements provide colours to fireworks?
(a) Zinc and sulphur
(b) Potassium and mercury
(c) Strontium and barium
(d) Chromium and nickel
Ans. (c) Strontium and Barium are mixed in fireworks in order to provide colours to them.
UPSC Previous Year Paper [2004]
30. Standard 18-carat gold sold in the market contains
(a) 82 parts gold and 18 parts other metals
(b) 18 parts gold and 82 parts other metals
(c) 18 parts gold and 6 parts other metals
(d) 9 parts gold and 15 parts other metals
Ans. (a) 18K gold contains 82 parts gold and 18 parts other metal. 18K gold is 75 per cent gold mixed with 25 per cent of other metals like copper or silver etc. Usually studded jewellery and other diamond jewellery is made in 18K gold. It is less expensive compared to 24K and 22K. This one has a slightly dull gold colour. Recognizing 18K jewellery is rather simple – you will see the item stamped with 18K, 18Kt, 18k or abbreviation similar to these. At times, 18K gold is marked by 750, 0.75 or a stamp similar to these in order to symbolise that the jewellery contains 75 per cent gold.
UPSC Previous Year Paper [2004]
31. Which one of the following is produced during the formation of photochemical smog?
(a) Hydrocarbons (b) Nitrogen Oxides
(c) Ozone (d) Methane
Ans. (c) Ground level Ozone, which is a secondary air pollutant, is created during formation of Photochemical smog. Photochemical smog is a condition that develops when primary pollutants (oxides of nitrogen and volatile organic compounds created from fossil fuel combustion) interact under the influence of sunlight to produce a mixture of hundreds of different and hazardous chemicals known as secondary pollutants. Ground level or “bad” ozone is not emitted directly into the air, but is created by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOC) in the presence of sunlight.
UPSC Previous Year Paper [2003]
32. Which one of the following statements is correct?
(a) Liquid Sodium is employed as a coolant in nuclear reactors
(b) Calcium carbonate is an ingredient of tooth paste
(c) Bordeaux mixture consists of Sodium sulphate and lime
(d) Zinc amalgams are used as a dental filling
Ans. (b) Abrasives typically include calcium carbonate, dehydrated silicia gels and hydrated aluminium oxides. Abrasive are integral constituents of toothpaste and hence, option (b) is true.
UPSC Previous Year Paper [2003]
33. Which one of the following statements is NOT correct?
(a) The presence of NACL increases the rate of setting of Plaster of Paris
(b) Gypsum is added to the cement to slow down its rate of setting
(c) All alkaline earth metals form hydrated salts
(d) Barium and Strontium are found free in nature
Ans. (d) Barium and Strontium are highly reactive elements. And due to its high chemical reactivity, both elements are never found in nature as a free element.
UPSC Previous Year Paper [2003]
34. With reference to ionic compounds, consider the following statements:
1. Ionic compounds are insoluble in alcohol.
2. Ionic compounds in the solid state are good conductors of electricity.
Which of these statements is/are correct?
(a) Only 1 (b) Only 2
(c) Both 1 and 2 (d) Neither 1 nor 2
Ans. (a) Ionic compounds typically have a low solubility in ethanol. This is because of the “like dissolves like” idea, which states that solutes will tend to dissolve in solvents with similar polarity. Ionic compounds in the solid state are bad conductors of electricity. Because as we know that particles in solid state are held by stronger interparticle force. Hence the particles in solid do not possess translatory motion, they can only vibrate about their mean position where as in molten state particles are held by not very strong inter-particle force. Hence, the particles in molten state possess translatory motion, they are free to move and they didn’t vibrate about their mean position. That`s why Ionic solid conduct electricity in molten state in form of their aqueous solution but not in solid state.
UPSC Previous Year Paper [2003]
35. Assertion (A): In the periodic table of chemical elements, bottom in a group.
Reason (R): In a group, the atomic radii generally increase
(a) Both A and R are individually true and R is the correct (b) Both A and R are individually true but R is not the (c) A is true but R is false
(d) A is false but R is true
Ans. (a) Electron affinity is always found to increase from top to increase from top to bottom in a periodic table. Electron affinity generally decreases down a group of elements because each atom is larger than the atom above it (this is the atomic radius trend). This means that an added electron is further away from the atom’s nucleus compared with its position in the smaller atom. With a larger distance between the negativelycharged electron and the positively-charged nucleus, the force of attraction is relatively weaker. Therefore, electron affinity decreases. Moving from left to right across a period, atoms become smaller as the forces of attraction become stronger. This causes the electron to move closer to the nucleus, thus increasing the electron affinity from left to right across a period.
UPSC Previous Year Paper [2003]
36. Consider the following statements:
The purpose of adding sodium sulphate and sodium silicate to the detergent in a washing powder is:
(1) to keep the washing powder dry.
(2) to maintain the alkalinity of the powder Which of these statements is/are correct?
(a) Only 1 (b) Only 2
(c) both 1 and 2 (d) Neither 1 nor 2
Ans. (b) Sodium silicate is used as water softener, added to inactivate hard water minerals.
UPSC Previous Year Paper [2003]
37. Assertion (A): Unsaturated fats are more reactive compared with the saturated fats.
Reason (R): Unsaturated fats have only single bonds in their structure.
(a) Both A and R are individually true and R is the correct (b) Both A and R are individually true but R is not the (c) A is true but R is false
(d) A is false but R is true
Ans. (c) Assertion is right but Reason is wrong.
UPSC Previous Year Paper [2003]
38. Assertion (A): Coal-based thermal power stations contribute to acid-rain.
Reason (R): Oxides of carbon are emitted when coal burns.
(a) Both A and R are individually true and R is the correct (b) Both A and R are individually true but R is not the (c) A is true but R is false
(d) A is false but R is true
Ans. (b) Coal based power plants are significant contributor of acid rains globally. Coal based power plants emits nitrous oxides and sulphur oxides which are the main causes of Acid rains and thus, a direct relation does exist between the number of coal based power plants and the frequency of acid rains. Coal based power plants does also produce oxides of carbon but as it is well known fact that the oxides of carbon does not play major role in acid rains. Hence, assertion and reasons both are individually correct but reason is not the correct explanation of assertion. B is the correct answer.
UPSC Previous Year Paper [2003]
39. Regarding the atom of a chemical element, the magnetic quantum number refers to:
(a) orientation (b) shape
(c) size (d) spin
Ans. (a) Magnetic Quantum Number specifies the orientation in space of an orbital of a given energy (n) and shape (l). This number divides the subshell into individual orbitals which hold the electrons; there are 2l+1 orbitals in each subshell.
UPSC Previous Year Paper [2003]
40. Which one of the following statements is correct?
(a) The boiling point of an aqueous solution is higher than that of pure water
(b) Addition of solutes to a solution causes an increase in its water potential
(c) The vapour pressure of the water in a solution is lower than that of pure water
(d) When a solution is separated from water by a semi permeable membrane, water movement can be prevented by applying pressure to the solution
Ans. (a) Aqueous solution have both a lower freezing point and a higher boiling point than pure water (Raoult’s law).
UPSC Previous Year Paper [2002]
41. Assertion (A): Synthetic detergents can lather well in hard water.
Reason (R): Synthetic detergents form soluble calcium and magnesium salts with hard water.
(a) Both A and R are individually true and R is the correct explanation of A
(b) Both A and R are individually true but R is not a correct explanation of A
(c) A is true but R is false
(d) A is false but R is true
Ans. (a) Detergents are sodium or potassium salts of sulphonic acid. Sodium or potassium being more reactive than calcium or magnesium displace them forming their water soluble salts.
UPSC Previous Year Paper [2002]
42. Match List I (Oxdiation number) with List II (The element) and select the correct answer using the codes given below this lists:
List I : List II
(Oxidation number) : (The element)
A. 2 : 1. Oxidation number of Mn in MnO2
B. 3 : 2. Oxidation number of S in H2S2O7
C. 4 : 3. Oxidation number of Ca in CaO
D. 6 : 4. Oxidation number of Al in NaAIH4 Codes:
A B C D
(a) 3 4 1 2 (b) 4 3 1 2
(c) 3 4 2 1 (d) 4 3 2 1
Ans. (a)
UPSC Previous Year Paper [2002]
43. Assertion (A): A Chemical reaction becomes faster at higher temperatures.
Reason (R): At higher temperatures, molecular motion becomes more rapid.
(a) Both A and R are individually true and R is the correct explanation of A
(b) Both A and R are individually true but R is NOT a correct explanation of A
(c) A is true but R is false
(d) A is fasle but R is true
Ans. (a) Temperature is the amount of kinetic energy possesed by the particles of an element. And a reaction occurs when two atoms or particles collide with each other. For example, when an atom of Na collides with an atom of Cl, NaCl is formed. Now, when the temperature raises, the particles have more kinetic energy and thus move faster. Moving faster implies that there will be more collisions per seconds. Thus, the reaction occurs faster. Hence, Assertion and Reason both are correct and R is the correct explanation of A.
UPSC Previous Year Paper [2001]
44. Match List I with List II and select the correct answer using the codes given below the Lists:
List I : List II
(Characteristic) : (Particle)
A. Zero mass : 1. Positron
B. Fractional charge : 2. Neutrino
C. Fractional spin : 3. Quark
D. Integral spin : 4. Phonon Codes:
A B C D
(a) 2 3 1 4 (b) 3 2 4 1
(c) 2 3 4 1 (d) 3 2 1 4
Ans. (b) Neutrinos have mass. Quark are mass less sub-atomic components. Phonon does not have integral spin.
UPSC Previous Year Paper [2001]
45. In an atom, the order of filling up of the orbitals is governed by
(a) Aufbau principle
(b) Heisenberg’s uncertainty principle
(c) Hund’s rule
(d) Pauli’s exclusion principle
Ans. (a) In an atom, the order of filling up of the orbitals is governed by Aufbau principle. The Aufbau principle states that, hypothetically, electrons orbiting one or more atoms fill the lowest available energy levels before filling higher levels (e.g., 1s before 2s). In this way, the electrons of an atom, molecule, or ion harmonize into the most stable possible electron configuration.
UPSC Previous Year Paper [2001]
46. Which one of the following is the correct sequence in increasing order of molecular weights of the hydrocarbons?
(a) Methane, ethane, propane and butane
(b) Propane, butane, ethane and methane
(c) Butane, ethane, propane and methane
(d) Butane, propane, ethane and methane
Ans. (a) Butane has the highest molecular weight and Methane has the least molecular weight. Propane does have greater molecular weight than ethane. Thus, correct increasing sequence is A.
UPSC Previous Year Paper [2001]
47. An aqueous solution of copper sulphate is acidic in nature because the salt undergoes
(a) Dialysis
(b) Electrolysis
(c) Hydrolysis
(d) Photolysis
Ans. (c) Because of hydrolysis it undergoes, the aqueous solution of copper sulphate is acidic in nature.
UPSC Previous Year Paper [2001]
48. Which one of the following is NOT radioactive?
(a) Astatine (b) Francium
(c) Tritium (d) Zirconium
Ans. (d) Zirconium is not a radioactive element. Zirconium is mainly used as a refractory and opacifier, although small amounts are used as an alloying agent for its strong resistance to corrosion. Zirconium forms a variety of inorganic and organometallic compounds such as zirconium dioxide and zirconocene dichloride, respectively. Five isotopes occur naturally, three of which are stable. Zirconium compounds have no known biological role.
UPSC Previous Year Paper [2001]
49. Consider the following statements with reference to the Periodic Table of chemical elements:
1. Ionisation potential gradually decreases along a period.
2. In a group of elements, electron affinity decreases as the atomic weight increases.
3. In a given period, electronegativity decreases as the atomic number increases.
Which of these statement(s) is/are correct?
(a) 1 only
(b) 2 only
(c) 1 and 3
(d) 2 and 3
Ans. (b) Ionisation Potential gradually increases along a period in periodic table. In a given period, electronegetivity increases as the atomic number increases.
UPSC Previous Year Paper [2001]
@50. The stones formed in human kidney consist mostly of
(a) calcium oxalate (b) sodium acetate
(c) magnesium sulphate (d) calcium
Ans. (a) Calcium is one component of the most common type of human kidney stones, calcium oxalate.
UPSC Previous Year Paper [2000]
51. Match List I with List II and select the correct answer using the codes given below the Lists:
List I : List II
A. German Silver : 1. Tin
B. Solder : 2. Nickel
C. Bleaching Powder : 3. Sodium
D. Hypo : 4. Chlorine Codes:
A B C D
(a) 1 2 4 3 (b) 2 1 3 4
(c) 1 2 3 4 (d) 2 1 4 3
Ans. (d) German silver or Nickel Silver is a metal alloy of copper with nickel and zinc. Zinc may not be always present. It is named for its silvery appearance, but contains no elemental silver. Solder is a low-melting alloy, especially one based on lead and tin or (for higher temperatures) on brass or silver, used for joining less fusible metals. Bleaching powder (CaOCl2) is made by just passing chlorine over slack lime.
UPSC Previous Year Paper [2000]
52. Most of the explosions in mines occur due to the mixing of
(a) hydrogen with oxygen
(b) oxygen with acetylene
(c) methane with air
(d) carbon dioxide with ethane
Ans. (c) Most of the explosion in mines occur due to the mixing of methane with the air present in the mines. Methane, the main component of natural gas, is combustible, and mixtures of about 5 percent to 15 percent in air are explosive. When air contains approximately 9.5 percent of methane (the most dangerous concentration), it reaches the perfect oxidation point, which means that the right amount of fuel is mixing with the right amount of oxygen. This produces water, carbon dioxide and a lot of amount of heat resulting in massive explosions. CH4 + 2O2 CO2 + 2H2O + Heat
UPSC Previous Year Paper [2000]
53. Soft drinks such as colas contain significant quantities of
(a) caffeine (b) nicotine
(c) tannin (d) rennin
Ans. (a) Soft drinks such as cola contain significant quantities of caffeine. Soft drinks typically contain 0 to 55 milligrams of caffeine per 12 ounce serving. By contrast, energy drinks, such as Red Bull, can start at 80 milligrams of caffeine per serving. The caffeine in these drinks either originates from the ingredients used or is an additive derived from the product of decaffeination or from chemical synthesis. Guarana, a prime ingredient of energy drinks, contains large amounts of caffeine with small amounts of theobromine and theophylline in a naturally occurring slow-release excipient.
UPSC Previous Year Paper [2000]
54. Which one of the following materials is very hard and very ductile?
(a) Carborundum (b) Tungsten
(c) Cast Iron (d) Nichrome
Ans. (d) Nichrome generally refers to any alloy of nickel, chromium, and often iron and/or other elements or substances. It is known to be very hard and very ductile. Nichrome alloys are typically used in resistance wire of heating elements.
UPSC Previous Year Paper [2000]
55. A small pouch containing silica gel is often found in bottles of medicine in tablet or powder form because silica gel
(a) kills bacteria
(b) kills germs and spores
(c) absorbs moisture
(d) absorbs all gases present inside the bottle
Ans. (c) Little packets of silica gel are found in all sorts of products because silica gel is a desiccant — it adsorbs and holds water vapor. In a wide range of products and foods like pepperoni, the lack of moisture can limit the growth of mold and reduce spoilage. In electronics it prevents condensation, which might damage the electronics. If a bottle of vitamins contained any moisture vapor and were cooled rapidly, the condensing moisture would ruin the pills. We find little silica gel packets in anything that would be affected by excess moisture or condensation.
UPSC Previous Year Paper [2000]
56. Aluminium surfaces are often ‘anodized’. This means the deposition of a layer of
(a) chromium oxide (b) aluminium oxide
(c) nickel oxide (d) zinc oxide
Ans. (b) Anodizing is an electrochemical process that converts the metal surface into a decorative, durable, corrosion-resistant, anodic oxide finish. Aluminum is ideally suited to anodizing, although other nonferrous metals, such as magnesium and titanium, also can be anodized. The anodic oxide structure originates from the aluminum substrate and is composed entirely of aluminum oxide (Al2O3). This aluminum oxide is not applied to the surface like paint or plating, but is fully integrated with the underlying aluminum substrate, so it cannot chip or peel. It has a highly ordered, porous structure that allows for secondary processes such as coloring and sealing.
UPSC Previous Year Paper [2000]
57. Assertion (A): Large cold storage plants use ammonia as refrigerant while domestic refrigerators use chlorofluorocarbons.
Reason (R): Ammonia can be liquified at ambient temperatures at low pressures.
(a) Both A and R are true, and R is the correct explanation of A
(b) Both A and R are true, but R is not a correct explanation of A
(c) A is true, but R is false
(d) A is false, but R is true
Ans. (a) Both are individually true and R is the correct explanation of A.
UPSC Previous Year Paper [2000]
58. Match List I (Industrial processes) with List II (Industry with which associated) and select the correct answer using the codes given below the Lists:
List I : List II
A. Cracking : 1. Rubber
B. Smelting : 2. Petroleum
C. Hydrogenation : 3. Copper
D. Vulcanization : 4. Edible fats Codes:
A B C D
(a) 3 2 1 4 (b) 2 3 4 1
(c) 2 3 1 4 (d) 3 2 4 1
Ans. (b)
UPSC Previous Year Paper [2000]
59. Canola refers to special type of oil seed mustard varieties bred for human consumption. The main characteristic of these varieties is that the
(a) seeds have very high oil content
(b) oil is rich in unsaturated fatty acids
(c) oil has long shelf-life
(d) oil has very low Erucic acid content
Ans. (a) Canola seeds have very high oil content. Canola oil is good for heart patients as they contain least saturated fats compared to other vegetative oils.
UPSC Previous Year Paper [2000]
60. Consider the following statements: Hard water is not suitable for
1. drinking.
2. washing cloths with soap.
3. use in boilers.
4. irrigating crops.
Which of these statements are correct?
(a) 1 and 3 (b) 2 and 3
(c) 1, 2 and 4 (d) 1, 2, 3 and 4
Ans. (b) Hard water is not a health hazard and therefore, has not been forbidden from drinking. Hard water can be used for irrigation purposes as well. Thus, B is the correct answer. On the other hand, hard water interferes with almost every cleaning task from laundering and dishwashing to bathing and personal grooming.
UPSC Previous Year Paper [2000]
61. The most reactive among the halogens is
(a) fluorine (b) chlorine
(c) bromine (d) iodine
Ans. (a) Fluorine is the most reactive element of all in halogen group. It is used to produce hydro fluoric acid that can cause itching on glass surface.
UPSC Previous Year Paper [1997]
62. Which one of the following has the highest fuel value?
(a) Hydrogen (b) Charcoal
(c) Natural Gas (d) Gasoline
Ans. (a) Hydrogen has the highest fuel value but is not used as fuel because of its very high explosive nature and very low ignition temperature.
UPSC Previous Year Paper [1997]
63. Which one of the following is paramagnetic in nature?
(a) Iron (b) Hydrogen
(c) Oxygen (d) Nitrogen
Ans. (c) Oxygen is paramagnetic in nature. The reason that it is paramagnetic is because the oxygen molecule has two unpaired electrons. Electrons not only go around the atom in their orbitals, they also spin, which creates a magnetic field. Unpaired electrons spin in the same direction as each other, which increases the magnetic field effect.
UPSC Previous Year Paper [1997]
64. Which one of the following is used as an anti-freeze for the automobile engines?
(a) Propyl alcohol (b) Ethanol
(c) Methanol (d) Ethylene glycol
Ans. (d) The most common water-based antifreeze solutions used in electronics cooling are mixtures of water and either ethylene glycol (EGW) or propylene glycol (PGW). The use of ethylene glycol has a longer history, especially in the automotive industry. An antifreeze is an additive which lowers the freezing point of a water-based liquid. An antifreeze mixture is used to achieve freezing-point depression for cold environments and also achieves boiling-point elevation (“anti-boil”) to allow higher coolant temperature.
UPSC Previous Year Paper [1997]
65. The offending substance in the liquor tragedies leading to blindness, etc. is
(a) ethyl alcohol
(b) amyl alcohol
(c) benzyl alcohol
(d) methyl alcohol
Ans. (d) Today the most common cause of blindness from drinking is methanol. Methanol, otherwise known as methyl alcohol or wood alcohol, can damage the optic nerve and even kill a person in high concentrations.
UPSC Previous Year Paper [1996]
66. The alpha-particle carries two positive charges. Its mass is very nearly equal to that of
(a) two protons
(b) an atom of helium
(c) sum of masses of two positrons and two neutrons
(d) two positrons as each positron carries a single positive charge
Ans. (b) Alpha-particle consists of two neutrons and two protons, and is thus identical to the nucleus of a helium atom. The rest mass of the alpha particle amounts to 4 × 6.64424 × 10–27 kg.
UPSC Previous Year Paper [1996]
67. Which one of the following elements is alloyed with iron to produce steel which can resist high temperatures and also have high hardness and abrasion resistance?
(a) Aluminium
(b) Chromium
(c) Nickel
(d) Tungsten
Ans. (b) Ferrochrome (FeCr) is an alloy of chromium and iron containing 50% to 70% chromium by weight. Over 80% of the world’s ferrochrome is utilized in the production of stainless steel which can resist high temperatures and also has high hardness and abrasion resistance.
UPSC Previous Year Paper [1996]
68. Which one of the following polymers is widely used for making bullet proof material?
(a) Polyvinyl chloride (b) Polyamides
(c) Polyethylene (d) Polycarbonates
Ans. (c) Polyethylene is widely used for making bullet proof materials.
UPSC Previous Year Paper [1995]
69. Which one of the following is a mixed fertilizer?
(a) Urea
(b) CAM
(c) Ammonium Sulphate
(d) NPK
Ans. (d) NPK fertilizers are three-component fertilizers providing nitrogen, phosphorus, and potassium. NPK rating is a rating system describing the amount of nitrogen, phosphorus, and potassium in a fertilizer. NPK ratings consist of three numbers separated by dashes (e.g., 10-10-10 or 16-4-8) describing the chemical content of fertilizers.
UPSC Previous Year Paper [1995]
70. Which one of the following pairs of materials serves as electrodes in chargeable batteries commonly used in devices such as torchlights, electric shavers, etc?
(a) Nickel and cadmium (b) Zinc and carbon
(c) Lead peroxide and lead
(d) Iron and cadmium
Ans. (b) Zinc and Carbon electrodes are used widely in dry cell, which are used in common home appliances such as torchlights, electric shavers, etc.
UPSC Previous Year Paper [1995]
71. The chemical used as a ‘fixer’ in photography is
(a) sodium sulphate (b) sodium thiosulphate
(c) ammonium persulphate
(d) borax
Ans. (b) Sodium thiosulphate is a popular ‘photography fixer’ used widely in the industry.
UPSC Previous Year Paper [1995]
72. ‘Yellow cake’, an item of smuggling across borders is
(a) a crude form of heroin
(b) a crude form of cocaine
(c) uranium oxide
(d) unrefined gold
Ans. (c) ‘Yellowcake’ is a type of uranium concentrate powder obtained from leach solutions, in an intermediate step in the processing of uranium ores. It is a step in the processing of uranium after it has been mined, before fuel fabrication or enrichment.
UPSC Previous Year Paper [1995]
73. ‘The final Agent Orange raid in Vietnam took place in 1970;.. areas have begun to bloom again. But 19 years after the war’s end, it seems plain that Agent Orange is killing and maiming human beings, something it never intended to do. The apparent toxic fall out from those clouds .. is a crop of human miseries including cancers, miscarriages and birth defects—that may persist for decades.” The offensive substance referred to in the above quotation is
(a) DDT used as insecticide
(b) a complex mixture of herbicides and weedicides used to increase agricultural output in the then South Vietnam under the US aid programme
(c) a complex mixture of DDT and other insecticides used as aerial sprays for protection against malaria and other tropical diseases
(d) dioxin used as defoliants
Ans. (b) Agent orange is one of the Herbicides and defoliants used by the US military as part of its herbicidal warfare program, operation Ranch hand during the Vietnam war. It is a mixture of herbicides 2, 4, 5,– T & 2, 4, – 0.
UPSC Previous Year Paper [1995]
74. Which one of the following is in the correct sequential order in which these appeared under simulated primitive earth condition?
(a) Methane, Hydrogen cyanide, nitriles, aminoacids
(b) Hydrogen cyanide, methane, nitriles, aminoacids
(c) Aminoacids, nitriles. Hydrogen cyanide, methane
(d) Nitriles, aminoacids, methane, Hydrogen cyanide
Ans. (b) In primitive earth conditions, hydrogen, cynide methane, nitriles, aminoacids etc are had been found.
UPSC Previous Year Paper [1994]
75. The main constituents of pearl are
(a) calcium carbonate and magnesium carbonate
(b) aragonite and conchiolin
(c) ammonium sulphate and sodium carbonate
(d) calcium oxide and ammonium chloride
Ans. (a)
UPSC Previous Year Paper [1994]
76. The basic reason for the extraordinary sparkle of a suitably cut diamond is that
(a) it has a very high transparency
(b) it has a very high refractive index
(c) it is very hard
(d) it has well-defined cleavage planes
Ans. (d) It has the maximum refractive index for any naturally found material. The basic reason for the extraordinary sparkle of a suitably cut diamond is that it has a very high refractive index. Which is given well defined clevage planes when cut.
UPSC Previous Year Paper [1994]
77. Galvanised iron sheets are protected from rusting due to the presence of a layer of
(a) lead (b) chromium
(c) zinc (d) tin
Ans. (c) Galvanised iron sheets are protected from rusting due to the presence of a layer of zinc.
UPSC Previous Year Paper [1994]
78. Monazite is an ore of
(a) zirconium (b) thorium
(c) titanium (d) iron
Ans. (b) Monazite is an important ore for thorium, lanthanum, and cerium. India, Madagascar, and South Africa have large deposits of monazite sands. The deposits in India are particularly rich in monazite.
UPSC Previous Year Paper [1994]
79. Water is a good solvent of ionic salts because
(a) it has a high boiling point
(b) it has a high dipole moment
(c) it has a high specific heat
(d) it has no colour
Ans. (b) Water is a good solvent due to its polarity. When an ionic or polar compound enters water, it is surrounded by water molecules. The relatively small size of water molecules typically allows many water molecules to surround one molecule of solute. The partially negative dipoles of the water are attracted to positively charged components of the solute, and vice versa for the positive dipoles.
UPSC Previous Year Paper [1994]
80. Which radioactive pollutant has recently drawn the attention of the public, due to its occurrence in the building material?
(a) Plutonium (b) Thorium
(c) Radon (d) Radium
Ans. (c) Recently, radon has drawn serious concern as a health threat due to its occurrence in the building material.
UPSC Previous Year Paper [1994]
81. Which one of the following is used for dating archaeological specimens in wood, bones and shells?
(a) Uranium-238
(b) Argon isotope
(c) Carbon-14
(d) Strontium-90
Ans. (c) Carbon dating uses the half-life of Carbon-14 to find the approximate age of certain objects like wood, bones and shells that are 40,000 years old or younger. It was developed right after World War II by Willard F. Libby and coworkers, and it has provided a way to determine the ages of different materials in archeology, geology, geophysics, and other branches of science. Age determinations can also be obtained from carbonate deposits such as calcite, dissolved carbon dioxide, and carbonates in ocean, lake, and groundwater sources.
UPSC Previous Year Paper [1993]
82. Given below is a diary of disasters involving hazardous chemicals. Which one of the following is correctly matched?
(a) 1959, Minamata/Nigiata, Japan: Leakage at pesticide plant
(b) 1976, Sevesor Italy: Mercury discharged into waterways
(c) 1984, Bhopal, India: Leakage of dioxin
(d) 1987, Kotka, Finland: Monochloro-benzene split In harbor
Ans. (d)
UPSC Previous Year Paper [1993]
83. The Government of India has totally banned the export of ‘Burnt Coal’ (Jhama), because it contains recoverable amount of a metal/element used in transistors. Which one is the element?
(a) Phophorus (b) Germanium
(c) Silicon (d) Tungsten
Ans. (b) Germanium is found in Jhama that is used in transistors.
UPSC Previous Year Paper [1993]
84. Which one of the following colloidal systems is represented by fog?
(a) Liquid in gas (b) Gas in liquid
(c) Solid in gas (d) Liquid in liquid
Ans. (a) Fog is liquid particles dispersed in a gas.
UPSC Previous Year Paper [1993]
85. Assertions (A): A mixture of salt and ice gives temperature below 0°C.
Reason (R): The salt raises the freezing point of ice.
In the context of the above two statements, which one of the following is correct?
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is NOT the correct explanation of A
(c) A is true but R is false
(d) A is false but R is true
Ans. (c) Adding salt to ice cause a temperature drop that slows the melting rate and increases the freezing rate. i.e. freezing point depresses.
UPSC Previous Year Paper [1993]
86. Though a few (gas-based) industries have already been established good reserves of natural gas in India remain unutilized. This vast resource of natural gas can be used in the production of
(a) fertilizers (b) carbide
(c) graphite (d) synthetic petroleum
Ans. (a) Almost 30% of natural gas supply in India is used for production of fertilizers.
UPSC Previous Year Paper [1993]
87. Vinegar is an aqueous solution of
(a) oxalic acid (b) citric acid
(c) acetic acid (d) hydrochloric acid
Ans. (d) Vinegar is 5% to 7% aqueous solution that contains acetic acid.
UPSC Previous Year Paper [1993]
88. Three important micronutrients essential for humans are
(a) Copper, zinc and iodine
(b) Zinc, copper and potassium
(c) Nitrogen, molybdenum and iodine
(d) Sulphur, copper and iron
Ans. (a) Micronutrients are those nutrients which we require in relatively small quantities. They are vitamins and minerals, and our good health requires them in milligram and microgram amounts. Copper, Zinc and Iodine are three most essential nutrients for humans.
UPSC Previous Year Paper [1992]
89. The gas used for artificial ripening of green fruits is
(a) Carbon dioxide (b) Ethane
(c) Hydrogen (d) acetylene (ethyne)
Ans. (d) Calcium carbide is used in some countries for artificially ripening fruit. When calcium carbide comes in contact with moisture, it produces acetylene gas, which is quite similar in reaction to the natural ripening agent, ethylene.
UPSC Previous Year Paper [1992]
90. Gypsum is added to cement clinker to
(a) Increase the tensile strength of the cement
(b) Bind the particles of calcium silicate
(c) Decrease the rate of setting of cement
(d) Facilitate the formation of colloidal gel
Ans. (c) Gypsum is added to cement clinker to decrease the rate of setting of cement. When cement is mixed with water, it becomes hard over a period of time. This is called setting of cement. Gypsum is often added to Portland cement to prevent early hardening or “flashsetting”, allowing a longer working time.
UPSC Previous Year Paper [1992]
91. Natural rubber is a plant product which is chemically known as
(a) Mucilage (b) Gum
(c) Latex (d) Resin
Ans. (c) Natural rubber is a plant product which is chemically known as ‘latex’.
UPSC Previous Year Paper [1992]
92. The variation of temperature with heating of a solid substance, heated at constant rate, is shown in the following figure
Which portion of the above graph represents melting change from solid to liquid?
(a) AB (b) BC
(c) CD (d) DE
Ans. (a)
UPSC Previous Year Paper [1992]
93. German silver is an alloy of
(a) copper, zinc and nickel
(b) copper, iron and tin
(c) iron, chromium and nickel
(d) copper, aluminium and nickel
Ans. (a) German silver or Nickel Silver is a metal alloy of copper with nickel and often but not always zinc. It is named for its silvery appearance, but contains no elemental silver. Other common names for this alloy are Paktong, New Silver and Alpacca.
UPSC Previous Year Paper [1992]
94. Which one of the following is an element?
(a) Ruby
(b) Sapphire
(c) Emerald
(d) Diamond
Ans. (d) Diamonds are usually ~ 99.95% Carbon, with trace elements like hydrogen, boron or nitrogen. So diamonds are crystalline mostly made of carbon, which is the element here. None of the given in options are element.
UPSC Previous Year Paper [1992]
95. Galvanising of sheet iron is done by dipping the sheet metal into molten
(a) Mercury (b) Cadmium
(c) Lead (d) Zinc
Ans. (d) Galvanising of sheet iron is done by dipping the iron sheet metal into motten zinc in order to prevent rusting. The zinc serves as a sacrificial anode, so that it cathodically protects exposed steel. This means that even if the coating is scratched the exposed steel will still be protected from corrosion by the remaining zinc.
UPSC Previous Year Paper [1992]
96. The minimum possible temperature beyond which matter cannot be cooled is
(a) -98.10° C
(b) -100.00° C
(c) -273.15° C
(d) -459.40° C
Ans. (c) The accepted minimum possible temperature beyond which matter cannot be cooled is -273.15° C. This temperature is also called as absolute zero temperature at which all forms of movement stop with internal energy becoming equal to zero.
UPSC Previous Year Paper [1992]
97. It has been observed that after-effects of low temperature treatment are helpful in promoting the flowering in certain plants. Through this the vegetative period of plant becomes short and early flowering takes place. This phenomenon is known as
(a) Photoperiodism
(b) Floreignation
(c) Vernalisation
(d) Heliotropism
Ans. (c) Vernalization (from Latin vernus, “of the spring”) is the induction of a plant’s flowering process by exposure to the prolonged cold of winter, or by an artificial equivalent. After vernalization, plants have acquired the ability to flower, but they may require additional seasonal cues or weeks of growth before they will actually flower.
UPSC Previous Year Paper [1992]
98. Elements having atomic number higher than ’92’ in the periodic table are known as
(a) Transitional elements
(b) Rare earth elements
(c) Transuranic elements
(d) Alkaline earth metals
Ans. (c) The transuranium elements (also known as transuranic elements) are the chemical elements with atomic numbers greater than 92 (the atomic number of uranium). All of these elements are unstable and decay radioactively into other elements. Super heavy elements: An important group of elements
UPSC Previous Year Paper [1991]
99. Some medicines are given in the form of capsules.
The capsules are made of
(a) Paper
(b) Gelatinous material
(c) Embryonic tissue
(d) Starch
Ans. (b) Capsules are made of high-quality beef gelatin and purified water.
UPSC Previous Year Paper [1991]
@100. Which of the following pairs of substances can be completely separated by sublimation?
(a) Sand and iodine
(b) Ammonium chloride and iodine
(c) Sand and sulfur
(d) Salt and sulfur
Ans. (a) Sublimation can be used to separate a mixture of solids in which one solid sublimes and the others do not. Sublimation is the process in which a heated solid goes directly into the gaseous phase without passing through the liquid phase.
UPSC Previous Year Paper [1991]
101. Atoms of the same element having the same atomic number but different atomic weight are called
(a) Isobars (b) Isotopes
(c) Polymers (d) Isomers
Ans. (b) Isotopes are atoms with the same number of protons but that have a different number of neutrons. Since the atomic number is equal to the number of protons and the atomic mass is the sum of protons and neutrons, we can also say that isotopes are elements with the same atomic number but different mass numbers.
UPSC Previous Year Paper [1991]
102. The chemical name of ‘Aspirin’ is
(a) Acetyl cynamide
(b) Acetyl salicylic acid
(c) Benzyl salicylate
(d) Tartaric acid
Ans. (b) Aspirin, also known as ‘acetylsalicylic acid’, has a chemical formula of C9H8O4.
UPSC Previous Year Paper [1991]
103. Assertion (A): Unlike photographic film, which can be used only once, video tapes can be reused several times.
Reason (R): Photography involves chemical change but video recording is a physical change.
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is not a correct explanation of A
(c) A is true but R is false
(d) A is false but R is true
Ans. (a)
UPSC Previous Year Paper [1990]
104. Paraffin is a by-product of
(a) Petroleum refining
(b) Processing of agricultural wastes
(c) Cottage industries involving beekeeping
(d) Leather industry
Ans. (a) Paraffin wax is a petroleum by-product created when crude oil is refined into gasoline during course of its fractional distillation. It is a white, odorless solid that is formed into 10 lb. slabs. Paraffin is the most commonly used wax for candle making.
UPSC Previous Year Paper [1990]
105. The process of retting in jute is
(a) Purely physical (b) Purely chemical
(c) Microbiological (d) Physicochemical
Ans. (a) Retting is a purely physical process in which the tied bundles of jute stalks are taken to the tank by which fibres get loosened and separated from the woody stalk.
UPSC Previous Year Paper [1990]
106. Assertion (A): Activated charcoal is used for decolourising sugar solution.
Reason (R): Activated charcoal absorbs the impurities on its surface.
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is not a correct explanation of A
(c) A is true but R is false
(d) A is false but R is true
Ans. (a) Activated charcoal consists of small, black beads or a solid black porous sponge. It is used in water filters, medicines that selectively remove toxins, and chemical purification processes. Activated charcoal is carbon that has been treated with oxygen. The treatment result in highly porous charcoal.
UPSC Previous Year Paper [1990]
107. Water which contains soluble salts of calcium and magnesium is known as
(a) Heavy water (b) Soft water
(c) Hard water (d) Mineral water
Ans. (c) Hard water contains soluble salts of calcium and magnesium particularly their carbonates and sulphates. Hard water, water that contains salts of calcium and magnesium principally as bicarbonates, chlorides, and sulfates.
UPSC Previous Year Paper [1990]
108. Sparkling red colour after the blast of fire crackers is due to the presence of
(a) Strontium (b) Sodium
(c) Sulphur (d) Magnesium
Ans. (c) Sparkling red color after the blast of fire crackers is due to the presence of sulphur. Sulfur or sulphur is the chemical element with atomic number 16, represented by the symbol S. It is an abundant, multivalent nonmetal. At normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8.
UPSC Previous Year Paper [1989]
109. The chief ingredient of the mosquito repellent cream is derived from
(a) Tulsi (b) Neem
(c) Lemon (d) Rice bran
Ans. (a) The chief ingredient of the mosquito repellent cream is derived from Tulsi. Tulsi is cultivated for religious and medicinal purposes, and for its essential oil. It is widely known across South Asia as a medicinal plant and an herbal tea, commonly used in Ayurveda, and has an important role within the Vaishnavite tradition of Hinduism, in which devotees perform worship involving tulsi plants or leaves.
UPSC Previous Year Paper [1989]
110. Sodium vapour lamps are preferred to incandescent lamps because of
(a) Higher efficiency
(b) Higher tolerance in voltage fluctuations
(c) Easy installation
(d) Higher intensity of illumination
Ans. (d) The light intensity of sodium vapor lamps is relatively high compared to other form of lightning. In addition, it is cheaper.
UPSC Previous Year Paper [1989]
111. The chemical name of ‘aspirin’ is
(a) Acetyl cyanamide (b) Acetyl Salicylic Acid
(c) Benzyl Salicylate (d) Tartaric Acid
Ans. (b) Acetylsalicylic Acid, also known by trade name Aspirin, is an acetyl derivative of salicylic acid that is a white, crystalline, weakly acidic substance, with melting point 137°C.
UPSC Previous Year Paper [1989]
112. The highest grade of coal, whose surface is shining and has the highest calorific value, is
(a) Lignite
(b) Peat
(c) Bituminous
(d) Anthracite
Ans. (d) Anthracite is the highest grade of coal whose surface shines and has the highest calorific value. However for domestic and industrious purposes bituminous coal is commonly used.
UPSC Previous Year Paper [1989]
113. Which of the following is not an alloy?
(a) Brass (b) Bronze
(c) Steel (d) Zinc
Ans. (d) Zinc is NOT an alloy. It is an element.
UPSC Previous Year Paper [1989]
114. Match the columns:
List I : List II
A. Bauxite : 1. Lead
B. Silicon : 2. Thorium
C. Galena : 3. Aluminium
D. Monazite : 4. Computer memory
Select the correct answer from the codes given below:
A B C D
(a) 3 4 1 2 (b) 4 2 1 3
(c) 3 1 4 2 (d) 2 4 3 1
Ans. (a) Bauxite is major ore of aluminum. Thorium is extracted from monazite. lead is extracted from Glena. Silicon is used in making of microchips used in computer.
UPSC Previous Year Paper [1988]
115. The newly discovered high-temperature superconductors are
(a) Metal alloys
(b) Pure rare-earth metals
(c) Ceramic oxides
(d) Inorganic polymers
Ans. (a) Researchers have discovered an unusual property of purple bronze that may point to new ways to achieve high temperature superconductivity. Purple bronze are metal alloys.
UPSC Previous Year Paper [1988]
116. Match the columns:
List 1 : List 2 Organic acids : Substances in which they are present
A. Lactic acid : 1. Lemon
B. Acetic acid : 2. Rancid butter
C. Citric acid : 3. Milk
D. Butyric acid : 4. Vinegar : 5. Wine
Select the correct answer from the codes given below:
A B C D
(a) 5 4 3 2 (b) 3 1 4 5
(c) 2 5 1 3 (d) 3 4 1 2
Ans. (d) Lactic acid is present in milk and its products. A dilute solution of acetic acid is vinegar. Citric present is find in lemon. Butyric acid is found in rancid butter.
UPSC Previous Year Paper [1988]
117. Which one of the following is a non-metallic mineral?
(a) Manganese (b) Magnesium
(c) Gypsum (d) Bauxite
Ans. (c) Gypsum is a non- metallic mineral.
UPSC Previous Year Paper [1988]
118. The drugs-caffeine, tannin and nicotine are
(a) Steroids (b) Cortisones
(c) Alkaloids (d) Mild alkalis
Ans. (c) The drugs-caffeine, tannin and nicotine are types alkaloids
UPSC Previous Year Paper [1988]
119. Assertion (A): A dry cell cannot be recharged.
Reason (R): The chemical reaction in a dry cell is reversible.
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is NOT a correct explanation of A
(c) A is true but R is false
(d) A is false but R is true
Ans. (c) A primary or dry cell battery is a one that is designed to be used once and then discarded. A dry cell battery contains electrolytes that sit in paste. As the primary cell is used, chemical reactions in the battery use up the chemical that generate the power, when they are gone, the battery stops producing electricity and becomes useless.
UPSC Previous Year Paper [1988]
120. Which of the following chemicals in automobileexhaust can cause cancer?
(a) Carbon monoxide
(b) Polycyclic hydrocarbons
(c) Lead
(d) Oxides of nitrogen
Ans. (d) Carbon monoxides, one of the major pollutant gases from automobile-exhaust can cause cancer. Oxides of nitrogen lead to formation of photo chemical smog which is also carcinogenic.
UPSC Previous Year Paper [1988]
121. Assertion (A): Red phosphorous is preferred to white phosphorous in the manufacture of matches.
Reason (R): Red phosphorous is non poisonous in nature.
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is NOT a correct explanation of A
(c) A is true but R is false
(d) A is false but R is true
Ans. (a) Phosphorus has three main allotropes: white, red and black. White phosphorus is poisonous and can spontaneously ignite when it comes in contact with air. For this reason, white phosphorus must be stored under water and is usually used to produce phosphorus compounds.
UPSC Previous Year Paper [1988]
122. Assertion (A): Detergents can easily remove oil and dirt from soiled garments.
Reason (R): Detergents increase the surface tension of water.
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is NOT a correct explanation of A
(c) A is true but R is false
(d) A is false but R is true
Ans. (c) Detergents easily remove oil and dirt from soiled garments. The surfactants it contains are made of molecules that have two different ends. One end is strongly attracted to water; the other is attracted to oily substances like grease. Adding detergent lowers the surface tension. That’s because detergent molecules have one end that sticks well to water (hydrophilic) and another that doesn’t, hydrophobic end. The ends that don’t stick well to water coat the needle (or piece of dirt, etc) leaving the other ends in the water. Modern detergents contain more than surfactants. Cleaning products may also contain enzymes to degrade protein-based stains, bleaches to de-color stains and add power to cleaning agents, and blue dyes to counter yellowing.
UPSC Previous Year Paper [1988]
123. Ice skating can be used to demonstrate that when ice is under pressure, its
(a) Melting point is lowered
(b) Melting point is raised
(c) Melting point remains unchanged
(d) Coefficient of friction with metal is reduced
Ans. (a) Classical physics explains that skating can be used to demonstrate that ice when under pressure, undergoes a decrease in its point’s melting.
UPSC Previous Year Paper [1988]
124. If there were no organic life on the Earth, the amount of oxygen in the atmosphere will
(a) Remain unchanged.
(b) Be approximately hundred per cent.
(c) Be almost nil.
(d) Be approximately fifty per cent.
Ans. (c) All organic (living) things contain carbon and play a role in the carbon cycle. When any organic thing dies, be it human, plant or animal, it releases carbon into the atmosphere. If there were no plants for herbivorous animals to eat, there would be a mass extinction of many animals. In turn, carnivorous animals that ate herbivores would also eventually die off. With the absence of plants in the carbon cycle, the primary way carbon dioxide is removed from the atmosphere would be gone and it would be difficult to remove carbon dioxide from the atmosphere to keep the cycle going.
UPSC Previous Year Paper [1988]
125. Main constituents of Biogas are
(a) Methane and Carbon dioxide
(b) Ethylene and Carbon dioxide
(c) Butane and Carbon monoxide
(d) Methane and Carbon monoxide
Ans. (a) The major constituent of biogas is methane CH4 (55- 70%), CO2 (30-45%) and some traces of gases such as H2S and ammonia.
UPSC Previous Year Paper [1987]
126. A biogas plant works to its maximum capacity when
(a) Conditions are aerobic and temperature is 40°C.
(b) Conditions are anaerobic and temperature is 40°C.
(c) Conditions are aerobic and sewage is supplied.
(d) Conditions are anaerobic and sewage is supplied.
Ans. (b) A biogas plant functions maximum under anaerobic conditions and high temperature (40°C is considered ideal).
UPSC Previous Year Paper [1987]
127. Urea is prepared by the chemical reaction of
(a) Ammonia and Carbon dioxide
(b) Ammonium sulphate and calcium chloride
(c) Acetamide and ethyl alcohol
(d) Chlorine and water
Ans. (a) Urea is also known as carbamide, is an organic compound of carbon, nitrogen, oxygen and hydrogen, with the formula NH2(CO)NH2 or CO[NH2]
2. Urea is produced commercially from two raw materials, ammonia and carbon dioxide.
UPSC Previous Year Paper [1987]
128. Chemical composition of pearl is
(a) Calcium carbonate
(b) Calcium carbonate and magnesium carbonate
(c) Calcium sulphate
(d) Calcium chloride
Ans. (a) The chemical composition of pearl is 82-86% calcium Carbonate, 10-14% conchiolin and 2-4% of water (CaCO3 and H2O). The refractive index range is between 1.530 – 1.685. The hardness on the Mohs scale is 3.5 – 4. Its specific gravity is 2.65-2.85
UPSC Previous Year Paper [1987]
129. Radioactive element which has been found to have large reserves in India is
(a) Thorium (b) Uranium
(c) Radium (d) Plutonium
Ans. (a) Thorium is a radioactive element which has been found in large reserves in India.
UPSC Previous Year Paper [1987]
130. The chemical name for urea is
(a) Aneurin (b) Chloroethene
(c) Carbamide (d) None of these
Ans. (c) The chemical name of Urea are Carbamide, carbonyl diamide, carbonyl diamine, diaminomethanal, diaminomethane. The chemical formula of Urea is CO(NH2)2.
UPSC Previous Year Paper [1987]
131. A new biofertiliser is
(a) Compost (b) Farmyard manure
(c) Blue green algae (d) Nitrates
Ans. (c) Blue Green algae is relatively new biofertlizer.
UPSC Previous Year Paper [1986]
132. Which of the following statements about ozone layer is correct?
(a) It converts UV radiations into electrical energy
(b) It protects the earth’s life forms by preventing the damaging UV radiations from reaching earth’s surface
(c) It is of uniform thickness
(d) None of the above
Ans. (b) Ozone layer found in lower stratosphere protects the earth’s life forms by preventing the damaging UV radiations from reaching earth’s surface.
UPSC Previous Year Paper [1986]
133. Assertion: Carbon dioxide in air is necessary for sustaining life Reason: Carbon dioxide is assimilated in carbohydrates in photosynthesis
(a) if A and R both are correct and R is the correct explanation of A
(b) if A and R both are correct but R is not the correct explanation of A
(c) if A is correct and R is incorrect
(d) if A is incorrect and R is correct
Ans. (a) Carbon Dioxide (CO2) is a natural constituent of the atmosphere with a density of 747 mg per cubic meter of air. Its concentration in the composition of air is roughly 0.04%; however, of all the organic compounds, carbon dioxide is by far the most important one for the sustainability of the biosphere (the whole of life on Earth). Without CO2 the life of photosynthetic organisms and animals would be impossible, given that CO2 provides the basis for the synthesis of organic compounds that provide nutrients for plants and animals. Carbon dioxide is assimilated into carbohydrates in photosynthesis
UPSC Previous Year Paper [1986]
134. Which of the following elements exists in maximum quantity in atmosphere?
(a) Oxygen (b) Hydrogen
(c) Carbon (d) Nitrogen
Ans. (d) Nitrogen (78%) is the most abundantly found in the Earth’s atmosphere.
UPSC Previous Year Paper [1986]
135. Which of the following is the organic matter of animal and vegetable origin in the soil?
(a) Humus (b) Vermiculite
(c) Fulminic Acid (d) None of the above
Ans. (a) Humus is dark, organic material that forms in soil when plant and animal matter decays. When plants drop leaves, twigs, and other material to the ground, it piles up. This material is called leaf litter. When animals die, their remains add to the litter.
UPSC Previous Year Paper [1986]
136. Assertion: Alkalies are used for washing utensils.
Reason: Alkalies are readily soluble in water.
(a) if A and R both are correct and R is the correct explanation of A
(b) if A and R both are correct but R is not the correct explanation of A
(c) if A is correct and R is incorrect
(d) if A is incorrect and R is correct
Ans. (a) Both assertion and reason are correct and R is the correct explanation of R. Alkalis are bases soluble in water. They are also known for their corrossive nature hence used in dish washing.
UPSC Previous Year Paper [1986]
137. In India, the problem of utilisation of agriculture wastes is in
(a) Conversion of starch into alcohol
(b) Conversion of sugar into carbohydrates
(c) Conversion of bran into molasses
(d) Conversion of cellulose into sugar
Ans. (a) The problem of utilisation of agriculture wastes is in conversion of starch into alcohol.
UPSC Previous Year Paper [1986]
138. Which of the following is a weedkiller?
(a) Insecticide (b) Methyl salicylate
(c) Heribicide (d) None of these
Ans. (c) A herbicide is a pesticide used to kill unwanted plants, thus could be used as weed killers. Selective herbicides kill certain targets while leaving the desired crop relatively unharmed. Herbicides used to clear waste ground are nonselective and kill all plant material with which they come into contact. Some plants produce natural herbicides, such as the genus Juglans (walnuts). Herbicides are widely used in agriculture and in landscape turf management.
UPSC Previous Year Paper [1985]
139. Match the columns:
A. Bauxite : 1. Copper
B. Monazite : 2. Uranium
C. Malachite : 3. Thorium
D. Pitchblende : 4. Aluminum
Select the correct answer from the codes given below:
A B C D
(a) 3 4 2 1 (b) 3 1 2 4
(c) 4 3 1 2 (d) 4 3 2 1
Ans. (d) Bauxite is a major ore of aluminum. Thorium is extracted from Monazite. Uranium is extracted from malachite and copper is produced from Pitch-blende.
UPSC Previous Year Paper [1985]
140. Match the columns:
A. Glass : 1. Phosphorus
B. Match : 2. Sodium chloride
C. Fertiliser : 3. Sodium silicate
D. Salt : 4. Potassium sulphate
Select the correct answer from the codes given below:
A B C D
(a) 3 4 2 1 (b) 3 1 4 2
(c) 2 3 1 4 (d) 4 3 2 1
Ans. (b) Sodium silicate is used to produce glasses. Phosphorous is used to manufacture match sticks. Potassium sulphate is a fertilizer and Sodium chloride is a major constituent of salt.
UPSC Previous Year Paper [1985]
141. Which of the following is not an alloy?
(a) Bronze (b) Brass
(c) Steel (d) Zinc
Ans. (d) Zinc is not an alloy.
UPSC Previous Year Paper [1984]
142. Micro-elements needed to increase soil fertility are
(a) Nitrogen, hydrogen and calcium
(b) Nitrogen, phosphorus and potassium
(c) Iron, calcium and potassium
(d) Manganese, copper and zinc
Ans. (d) Micronutrients are those nutrients that are required by plants in very miniscule scale. Manganese, copper and zinc, etc. are some of essential micronutrients Macronutrients and Micro-nutrients: Somewhat arbitrarily, a dividing line is drawn between those nutrients required in greater quantities, macronutrients, and those elements required in smaller quantities, micronutrients. This division does not mean that one nutrient element is more important than another, just that they are required in different quantities and concentrations. On the table above, the dividing line is typically drawn between S and Cl, meaning that: Macronutrients: N, K, Ca, Mg, P, and S, and Micronutrients: Cl, Fe, B, Mn, Zn, Cu, Mo, and Ni
UPSC Previous Year Paper [1984]
143. Chlorine is
(a) A rare earth element
(b) A halogen
(c) A noble gas
(d) Coinage metal
Ans. (b) Chlorine is a member of halogen group.
UPSC Previous Year Paper [1984]
144. Which of the following is an insecticide?
(a) TNT (b) DDT
(c) Salicylic acid
(d) Ammonium phosphate
Ans. (b) DDT (Dichlorodiphenyltrichloroethane) is an insecticide that has been used to control the population of anopheles mosquito.
UPSC Previous Year Paper [1984]
145. Solution of washing soda in water is
(a) Acidic (b) Basic
(c) Neutral (d) Sour
Ans. (a) Sodium carbonate (also known as washing soda, soda ash and soda crystals), Na2CO3.10H2O is the watersoluble sodium salt of carbonic acid.
UPSC Previous Year Paper [1984]
146. The tape of the tape-recorder is coated with
(a) Cooper sulphate (b) Mica
(c) Ferromagnetic powder
(d) Zinc oxide
Ans. (c) Tape recorder, device for recording information on strips of plastic tape (usually polyester) that are coated with fine particles of a magnetic substance, usually an oxide of iron, cobalt, or chromium. The coating is normally held on the tape with a special binder.
UPSC Previous Year Paper [1984]
147. The internal antenna of a transistor set is made of
(a) Iron (b) Ferro-chrome
(c) Copper (d) Alnico
Ans. (b) The internal antenna of transistor is made of Ferrochrome.
UPSC Previous Year Paper [1983]
148. Radio carbon dating process is used to know the age of
(a) Fossils (b) Plants
(c) Rocks (d) All of these
Ans. (d) Radiocarbon dating (also referred to as carbon dating or carbon-14 dating) is a method for determining the age of an object containing organic material by using the properties of radiocarbon (14 C), a radioactive isotope of carbon. Thus, whatever object contains organic matter, its age can be calculated with the help of Radiocarbon dating technique.
UPSC Previous Year Paper [1983]
149. The common ore of aluminium is
(a) Bauxite (b) Chromite
(c) Cryolite (d) Monazite
Ans. (a) Bauxite ore is the world’s main source of aluminum. Bauxite is a rock formed from a reddish clay material called laterite soil and is most commonly found in tropical or subtropical regions. Bauxite is primarily comprised of aluminum oxide compounds (alumina), silica, iron oxides and titanium dioxide.
UPSC Previous Year Paper [1983]
@150. Arrange the following fertilisers according to the decreasing order of their nitrogen content
1. Ammonium sulphate
2. Ammonium nitrate
3. Potassium nitrate
4. Urea
Select the correct answer using the codes given below:
(a) 4, 2, 3, 1 (b) 4, 2, 1, 3
(c) 4, 3, 2, 1 (d) 2, 4, 3, 1
Ans. (a) (a) is the correct order. Ammonium sulphate : (NH4)2SO4 Ammonium nitrate : NH4NO3 Potassium nitrate : KNO3 Urea : CO (NH2)2
UPSC Previous Year Paper [1983]
151. Aspirin is a
(a) Pain reliever (b) Sedative
(c) Cortisone (d) Soporific
Ans. (a) Aspirin is a painkiller which can be taken to relieve pain such as headache, toothache and period pain. It is also suitable to treat cold and ‘flu-like’ symptoms, and to reduce a high temperature (fever). It can be taken by adults and children over 16 years of age, but it is not suitable for younger children. In the past, aspirin has also been used to reduce pain and inflammation in rheumatic conditions, but other medicines are now usually preferred.
UPSC Previous Year Paper [1983]
152. In a fluorescent tube which of the following components are found?
(a) Mercury vapour
(b) Argon and carbon dioxide
(c) Helium and oxygen
(d) Argon and neon
Ans. (a) Fluorescent lamps work by ionizing mercury vapor in a glass tube. This causes electrons in the gas to emit photons at UV frequencies. The UV light is converted into standard visible light using a phosphor coating of zinc on the inside of the tube. The most common fluorescent lamp is the hot cathode tube.
UPSC Previous Year Paper [1983]
153. Helium is used for respiration in deep water instead of nitrogen because
(a) It is heavier than nitrogen
(b) It is lighter than nitrogen
(c) It mixes less In blood than nitrogen
(d) It helps oxygen burn more quickly
Ans. (c) The main reason for adding helium to the breathing mixture is to reduce the proportions of nitrogen and oxygen below those of air, to allow the gas mix to be breathed safely on deep dives. A lower proportion of nitrogen is required to reduce nitrogen narcosis and other physiological effects of the gas at depth.
UPSC Previous Year Paper [1983]
154. Which one is a high yielding variety of rice?
(a) 1R-8 (b) 1R-21
(c) K-64 (d) M-986
Ans. (b)
UPSC Previous Year Paper [1983]
155. For artificial insemination the semen of a bull should be stored in
(a) Cold water (b) Ice
(c) Liquid nitrogen (d) Liquid oxygen
Ans. (c) For artificial insemination the semen of a bull should be stored in liquid nitrogen (cryopreservation).
UPSC Previous Year Paper [1983]
156. Arrange the following in the decreasing order of their carbon content
1. Cast iron
2. Wrought iron
3. Steel
Select the correct answer using the codes given below:
(a) 1, 2, 3 (b) 2, 1, 3
(c) 3, 2, 1 (d) 1, 3, 2
Ans. (a) The carbon content of steel is between 0.002% and 2.1% by weight for plain iron–carbon alloys. These values vary depending on alloying elements such as manganese, chromium, nickel, iron, tungsten, carbon and so on. Basically, steel is an iron-carbon alloy that does not undergo eutectic reaction. Steel has the least carbon content. Cast iron is a group of iron-carbon alloys with carbon content greater than 2%. Therefore it is difficult ot weld cast iron.
UPSC Previous Year Paper [1983]
157. In a remote Indian village with a scarcity of fuel, the people draw water from a well. They should be advised before drinking water to
(a) Boil it
(b) Use ion exchange resins
(c) Use solar stills for distilling
(d) Use potassium permanganate for purifying the water
Ans. (d) Potassium permanganate can be used for purifying the water, if there is fuel scarcity and water could not be boiled.
UPSC Previous Year Paper [1983]
158. Assertion: Galvanised iron pipes do not rust easily Reason: Zinc has a higher rate of oxidation than iron.
(a) If both A and R are true but R is not the reason for A
(b) If both A and R are true but R is the reason for A
(c) If neither A nor R is correct
(d) If A is correct but R is wrong
Ans. (b) Zinc is most commonly used as an anticorrosion agent, and galvanization (coating of iron and steel) is the most familiar form. Zinc is more reactive than iron or steel and thus will attract almost all local oxidation until it completely corrode away. A protective surface layer of oxide and carbonate (Zns (OH)6 (Co3)2) from as zinc corrode.
UPSC Previous Year Paper [1983]
159. The dress made out of which of the following is safe to wear while cooking?
(a) Nylon (b) Terylene
(c) Silk (d) Cotton
Ans. (d) Cotton can catch fires but do not get sticky instantly with the skin and thus, is preferred as clothing during cooking unlike synthetic fabric.
UPSC Previous Year Paper [1982]
160. The substance generally used in the tip of safety match stick is
(a) Red phosphorus
(b) Sodium
(c) Yellow phosphorus
(d) Antimony trisulphide
Ans. (a) Red phosphorous is generally used in the tip of safety match stick.
UPSC Previous Year Paper [1982]
161. The process by which metal surface is coated with thin layer of zinc is called
(a) Vulcanising (b) Galvanising
(c) Electroplating (d) None of these
Ans. (b) Galvanization is the process of applying a protective zinc coating to steel or iron, to prevent rusting.
UPSC Previous Year Paper [1982]
162. Which of the following is useful in the chemistry of photography?
(a) Silver bromide
(b) Aluminium hydroxide
(c) Sodium chloride
(d) Potassium nitrate
Ans. (a) Silver bromide is used in photography as a component of an emulsion that helps develop a photographic image. Silver bromide is sensitive to light, and when suspended in gelatin, silver bromide’s grains create a photographic emulsion. When exposed to light, silver bromide decomposes and as a result, it preserves a photographic image.
UPSC Previous Year Paper [1982]
163. Ozone present in the ozone layer of the atmosphere is important because
(a) It gives oxygen on dissociation
(b) It shields other gases
(c) It helps in the growth of the plants by absorbing a large proportion of the sun’s ultraviolet radiations
(d) None of these
Ans. (c) Ozone layer helps in preventing ultraviolet rays from reaching to earth’s surface. But this does not affect growth of plants upto a certain limit. In –fact, in lower amount ultraviolet rays increase the rate of photosynthesis which may result in increased growth of plants.
UPSC Previous Year Paper [1982]
164. Gasohol is mixture of gasoline and
(a) Ethyl alcohol (b) Methyl alcohol
(c) Kerosene (d) Butyl alcohol
Ans. (a) Gasohol is a mixture of one part ethanol (commonly known as grain alcohol” or beverage alcohol) and nine parts unleaded gasoline.
UPSC Previous Year Paper [1982]
165. The chief constituent of gobar gas is
(a) Hydrogen (b) Nitrogen
(c) Ethane (d) Methane
Ans. (d) The chief constituent of Gobar gas is Methane. The Gobar gas is also known as biogas. Biogas is a fuel gas, a mixture consisting of 65% methane (CH(d) and of 35% CO2. It is a renewable energy resulting from biomass. Biogas Organic household waste Farm yard waste Bio Gas system High-quality fertilizer
UPSC Previous Year Paper [1982]
166. After sowing seeds, the fertilizers used are
(a) Phosphates (b) Nitrates
(c) Green manures (d) All of these
Ans. (d) After sowing seeds all of the above fertilizers can be used.
UPSC Previous Year Paper [1982]
167. Diamond and Emerald contain
(a) Carbon and silicon
(b) Carbon and zinc
(c) Silicon, aluminium and beryllium
(d) Carbon and calcium
Ans. (c) Diamond and Emerald both contain Silicon, Aluminium and Beryllium.
UPSC Previous Year Paper [1982]
168. Which of the following statements is true?
(a) Both salinity and density of sea increase with depth
(b) Both salinity and density of sea decrease with depth
(c) Salinity increases but density of sea decreases with depth
(d) Salinity decreases but density of sea increases with depth
Ans. (d) There are two main causes of salinity of seawater- Chemicals, in seawater that make it salty and most of them get there from rivers carrying chemicals dissolved out of rock and soil, and the other is rate of evaporation. More the rate of evaporation,more the salinity. Thus, the surface of any water body essentially has the highest salinity. However, the case of density is quite opposite. The density of water depends upon its constituents. It also depends upon its temperature. The density of water increases with the increasing depth. However, after a certain depth they tends to be uniform for further depth.
UPSC Previous Year Paper [1981]
169. What is done to raise the dough while making bread?
(a) Alcohol is added
(b) Yeast is added
(c) Carbon dioxide is passed
(d) Air is passed
Ans. (b) Yeast is added during bread making in order to raise the dough. The main purpose of yeast is to serve as a catalyst in the process of fermentation, which is essential in the making of bread. The purpose of any leavener is to produce the gas that makes bread rise. Yeast does this by feeding on the sugars in flour, and expelling carbon dioxide in the process. C6H12O6 Yeast 2C2H5OH + 2CO2 The process lays the basic foundation of brewery and bakery industreis.
UPSC Previous Year Paper [1981]
170. In what sequence are the following obtained from a natural gas well?
1. Natural Gas
2. Water
3. Crude oil Codes:
(a) 1, 3, 2 (b) 1, 2, 3
(c) 3, 2, 1 (d) 2, 1, 3
Ans. (a) Because water is denser than oil. Therefore, it lies below the surface of oil.
UPSC Previous Year Paper [1981]
171. Which of the following is commonly present in the acids?
(a) Oxygen
(b) Hydrogen
(c) Sulphur
(d) Nitrogen
Ans. (b) Hydrogen is most commonly found in the acids. The basicity of a chemical depends on the number of hydrogen ions present as compared to hydroxide ions.
UPSC Previous Year Paper [1981]
172. Gypsum is added to the soil?
(a) To increase the alkalinity
(b) To decrease the acidity
(c) To decrease the alkalinity
(d) As an insecticide
Ans. (b) Gypsum is added in soil for its many advantages. Gypsum can treat increased soil acidity.
UPSC Previous Year Paper [1981]
173. Why camphor disappears when kept on a plate?
(a) It sublimes
(b) It reacts with the metal of the container
(c) It reacts with the gases of the air
(d) None of the above
Ans. (a) Camphor sublimes from its solid state to gaseous state. This property allows it to completely disappear from its solid state to very small particles suspended in air. • sublimation • Sublimation is the transition of a substance directly from the solid to the gas phase without passing through the intermediate liquid phase. • Sublimation is a type of phase transition, or a change in a state of matter, just like melting, freezing, and evaporation. Through sublimation, a substance changes from a solid to a gas without ever passing through a liquid phase. Dry ice (solid CO2) provides a common example of sublimation.
UPSC Previous Year Paper [1981]
174. The chief constituent of gabar gas is
(a) Methane (b) Carbon dioxide
(c) Acetylene (d) Ethylene
Ans. (a) The chief constituent of Gobar gas or Biogas is Methane.
UPSC Previous Year Paper [1980]
175. Dry ice is
(a) Solid carbon dioxide (b) Ice dust
(c) Liquified nitrogen (d) Liquified hydrogen
Ans. (a) Solid carbon dioxide is also known as ‘Dry Ice’. It sublimes on warming.
UPSC Previous Year Paper [1980]
176. The heater element in an electric iron is made of
(a) Nichrome (b) Tungsten
(c) Copper (d) Iron
Ans. (a) Nichrome: Most heating elements use Nichrome 80/ 20 (80% nickel, 20% chromium) wire, ribbon, or strip. Nichrome 80/20 is an ideal material, because it has relatively high resistance and forms an adherent layer of chromium oxide when it is heated for the first time.
UPSC Previous Year Paper [1980]
177. What is mainly obtained from bauxite?
(a) Copper (b) Aluminium
(c) Iron (d) Gold
Ans. (b) Bauxite (Al2O3.2H2O) is the main ore of aluminum.
UPSC Previous Year Paper [1980]
178. When iron rusts, the weight
(a) Increases
(b) Decreases
(c) Remains the same
(d) First increases then decreases
Ans. (a) Corrosion is the deterioration of a metal. When iron corrode an oxide will form on the surface exposed to the corrosive medium (water, air.) and the weight increase.
UPSC Previous Year Paper [1980]
179. Municipal water in India is generally treated with
(a) Chlorine
(b) Potassium permanganate
(c) Sodium Chloride
(d) Sodium Carbonate
Ans. (a) Muncipal water in India is treated with chlorine for its water cleansing properties
UPSC Previous Year Paper [1980]
180. Which substance is commonly used in refrigerators?
(a) Freon (b) Oxygen
(c) Ammonia (d) Sulphur dioxide
Ans. (a) Freon is most commonly used in refrigrators.
UPSC Previous Year Paper [1980]
181. If a large number of people are enclosed in a room, then
(a) Oxygen decreases and carbon dioxide increases
(b) Oxygen increases and carbon dioxide decrease
(c) Both oxygen and carbon dioxide decrease
(d) Both oxygen and carbon dioxide increase
Ans. (a) If a large number of people is enclosed in a tiny room, the level of oxygen in the room would decrease whereas the level of carbon dioxide would go up due to increased respiration in crowd and less source of oxygen.
UPSC Previous Year Paper [1979]
182. Gobar gas contains mainly
(a) Carbon dioxide (b) Methane
(c) Ethylene (d) Carbon monoxide
Ans. (b) Gobar gas mainly contains methane. Gobar gas is primarily methane (CH4) and carbon dioxide (CO2) and may have small amounts of hydrogen sulfide (H2S), moisture and siloxanes.
UPSC Previous Year Paper [1979]
183. The temperature for pasteurisation of milk is selected so as to
(a) Kill the micro-organisms
(b) Kill all bacteria
(c) Store it for long time without coagulation
(d) Kill the micro organisms and other harmful bacteria
Ans. (c) Heating milk to a high temperature and then quickly cooling it before bottling or packaging it could keep it fresh for longer. The process of pasteurisation involves heating milk to 71.7°C for at least 15 seconds (and no more than 25 seconds). Because of the nature of the heat treatment it sometimes referred to as the ‘High Temperature Short Time’ (HTST) process. Once the milk has been heated, it is then cooled very quickly to less than 3°C. The equipment which is used to heat and cool the milk is called a ‘heat exchanger’.
UPSC Previous Year Paper [1979]
184. The density of sea water is highest as
(a) Depth increases and salinity increases
(b) Depth decreases and salinity increases
(c) Depth increases and salinity decreases
(d) Depth decreases and salinity decreases
Ans. (a) The density of sea water depends upon. • Temperature • Salinity More the temperature lesser the density, more the salinity, more the density. Since, the temperature of sea-water decreases with increasing depth and salinity decreases, option (a) is the correct answer.
UPSC Previous Year Paper [1979]
185. Age of a tree can be determined
(a) By counting the number of rings
(b) By thickness of the bark
(c) By bulk of the tree
(d) By number of leaves
Ans. (a) The alternate number of spring and autumn ring i.e. dark and light wood indicates the age of a tree.
UPSC Previous Year Paper [1979]
186. What is the most important factor for the growth of pests in stored grains?
(a) The moisture of grains
(b) The temperature of grains
(c) The moisture and temperature of grains
(d) None of the above
Ans. (c) Temperature and moisture are two most important factors for growth of microorganisms in the grains.
UPSC Previous Year Paper [1979]
187. Which of the following metals is used in the electromagnets?
(a) Soft iron (b) Stainless steel
(c) Cobalt (d) Copper
Ans. (a) Soft iron is used to make electromagnets because it loses its magnetism as soon as the current stops flowing. Soft iron is said to form a temporary magnet. The soft iron inside the coil makes the magnetic field stronger because it becomes a magnet itself when the current is flowing.
UPSC Previous Year Paper [1979]
188. One litre of cold air weighs heavier than the dry air (1 Lit) because of the
(a) Increased number of collisions between the molecules
(b) Increased number of molecules at low temperature
(c) Greater energy of molecules at high temperature
(d) Lower energy of molecules at high temperature
Ans. (b) Cold air is much heavier than warm air and this is the basis for much of what we call weather. Cold air is denser than warm air. The molecules are packed closer together. The amount of water vapor in the air also affects the density of the air. The more water vapor that is in the air, the less dense the air becomes. That is why cold, dry air is much heavier than warm, humid air. You may have heard that a baseball or a golf ball will travel further on a warm, humid day than it would on a cold, dry day. Since the warm, humid air is less dense, the ball travels through it with less friction.
UPSC Previous Year Paper [1979]