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Part 048 – Chemistry Previous Year Questions

Q1. Sodium bicarbonate is commercially known as
(a) Washing soda
(b) Baking soda
(c) Caustic soda
(d) Soda lime
Ans: (b) Baking Soda is Sodium bicarbonate or sodium hydrogen carbonate. It is primarily used in cooking (baking), as a leavening agent. It reacts with acidic components in batters, releasing carbon dioxide, which causes expansion of the batter and forms the characteristic texture and grain in pancakes, cakes, quick breads, soda bread, and other baked and fried foods.

Q2. Coal is formed from

(a) crude oil
(b) deposit of animal waste
(c) coke
(d) compressed and hardened biomass
Ans: (d) A fossil fuel, coal forms when dead plant matter is converted into peat, which in turn is converted into lignite, then sub-bituminous coal, after that bituminous coal, and lastly anthracite. This involves biological and geological processes that take place over a long period.

Q3. Commercial Vaseline is derived from

(a) plant gums (b) coal tar
(c) wool wax (d) petroleum
Ans: (d) Vaseline is a brand of petroleum jelly based products owned by Anglo-Dutch company Unilever. While Vaseline can be used as a lubricant, it is also a useful moisture insulator for local skin conditions characterized by tissue dehydration. Vaseline helps protect minor cuts and burns.

Q4. Colour imparted to the Bunsen flame by strontium salt is

(a) bluish green
(b) apple-green
(c) brick red
(d) crimson red
Ans: (d) A flame test is performed by introducing a sample into the blue flame of a bunsen burner and noting any change in the colour of the flame. The tests can be used to detect the presence of some metallic elements in salts. With strontium salt, the colour of Bunsen flame ranges from crimson to red.

Q5. A potato tuber has been cut into two halves. A few drops of iodine solution are placed on the cut surface of one of the halves.
What colour change will be noticed?

(a) From brown to blue-black
(b) From brown to orange-red
(c) From blue to pink
(d) From pink to blue-green
Ans: (a) The Iodine test is used to test for the presence of starch. Iodine solution — iodine dissolved in an aqueous solution of potassium iodide — reacts with the starch producing a purple black colour.

Q6. Tear gas used by the police to disperse the mob contains

(a) Carbon dioxide
(b) Chlorine
(c) Ammonia
(d) Hydrogen sulphide
Ans: (b) Tear gas, formally known as a lachrymatory agent, is a possibly lethal chemical weapon that stimulates the corneal nerves in the eyes to cause tears, pain, and even blindness. The compound 2- chlorobenzalmalononitrile (chemical formula: C10H5ClN2), is the defining component of a “tear gas” commonly referred to as CS gas, which is used as a riot control agent.

Q7. Epsom salt is used

(a) as purgative
(b) in softening water
(c) in paper industry
(d) in making tooth paste
Ans: (a) Magnesium sulfate is an inorganic salt (chemical compound) containing magnesium, sulfur and oxygen which is commonly called Epsom Salt. Because like other salts, it withdraws water from cells, Epsom salt is used as a fast-acting purgative in some types of poisoning, to draw water into the intestines, thus, reducing constipation; to withdraw toxins from the body; and to draw fluid from the brain in cases of cerebral edema.

Q8. The common refrigerant in domestic refrigerator is

(a) Neon (b) Oxygen
(c) Nitrogen (d) Freon
Ans: (d) Common refrigerants used in domestic refrigerators are freon, neon and nitrogen. It flows through four components of refrigerator again and again. These four components are cooling chamber, compressor, heat exchanger and expander.

Q9. The chemical name of “laughing gas’ is

(a) Nitric oxide
(b) Nitrogen dioxide
(c) Nitrogen pentoxide
(d) Nitrous oxide
Ans: (d) Nitrous oxide, commonly known as laughing gas, is a chemical compound with the formula N2O. It is used in surgery and dentistry for its anesthetic and analgesic effects. It is known as “laughing gas” due to the euphoric effects of inhaling it, a property that has led to its recreational use as a dissociative anesthetic.

Q10. Brass is an alloy of

(a) Lead and tin
(b) Zinc and copper
(c) Antimony, tin and lead
(d) Zinc, tin and copper
Ans: (b) Brass is an alloy of copper and zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties. By comparison, bronze is principally an alloy of copper and tin. Bronze does not necessarily contain tin, and a variety of alloys of copper, including alloys with arsenic, phosphorus, aluminium, manganese, and silicon, are commonly termed “bronze”

Q11. The chemical name of rat poison is

(a) zinc oxide
(b) potassium cyanide
(c) lead nitrate
(d) zinc phosphide
Ans: (d) Zinc phosphide is used as a rodenticide. A mixture of food and zinc phosphide is left where the rodents can eat it. The acid in the digestive system of the rodent reacts with the phosphide to generate the toxic phosphine gas.

Q12. Which one of the following pairs is NOT correctly matched?

(a) Haematite : Copper
(b) Bauxite : Aluminium
(c) Monazite : Thorium
(d) Pitchblende : Uranium
Ans: (a) Haematite is the mineral form of iron oxide (Fe2O3), one of several iron oxides. It is mined as the main ore of iron. Hematite is harder than pure iron, but much more brittle.

Q13. Which of the following is used for refrigeration?

(a) Sulphur dioxide
(b) Chlorine
(c) Freon
(d) Phosphine
Ans: (c) Common refrigerants used in domestic refrigerators are Freon, neon and nitrogen. It flows through four components of refrigerator again and again.

Q14. Which of the following is used to denature ethanol ?

(a) Methyl alcohol
(b) Propyl alcohol
(c) Phenol
(d) Methane
Ans: (a) Denatured alcohol is ethanol that has additives to make it undrinkable (poisonous), to discourage recreational consumption. Different additives are used to make it difficult to use distillation or other simple processes to reverse the denaturation. Methanol is commonly used both because its boiling point is close to that of ethanol and because it is toxic.

Q15. The charcoal used to decolourise brown sugar solution is

(a) Wood charcoal
(b) Coconut charcoal
(c) Animal charcoal
(d) Sugar charcoal
Ans: (c) A special characteristic of animal charcoal is its power to remove substances from solution. A brown solution of raw sugar is decolourized when boiled with animal charcoal. Other substances that are similarly removed from solution are indigo, litmus, iodine, the colouring-matter of red wine, the brown matter of peaty water or sewage, astringent principles, and certain basic salts, etc.

Q16. The gas which is mainly responsible for the green house effect is:

(a) Ozone
(b) Oxygen
(c) Carbon dioxide
(d) Carbon monoxide
Ans: (c) A greenhouse gas (sometimes abbreviated GHG) is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The primary greenhouse gases in the Earth’s atmosphere are water vapour, carbon dioxide, methane, nitrous oxide, and ozone.

Q17. Which one of the following is used for dating very old objects of archaeological importance?

(a) Phosphorus-31
(b) Tritium
(c) Radium
(d) Carbon-14
Ans: (d) Radiocarbon dating (usually referred to as simply carbon dating) is a radiometric dating method that uses the naturally occurring radioisotope carbon-14 (14C) to estimate the age of carbon-bearing materials up to about 58,000 to 62,000 years. After plants die or they are consumed by other organisms (for example, by humans or other animals), the incorporation of all carbon isotopes, including 14C, stops. Thereafter, the concentration (fraction) of 14C declines at a fixed exponential rate due to the radioactive decay of 14C.

Q18. The main constituent of natural gas is

(a) Methane (b) Ethane
(c) Butane (d) Propane
Ans: (a) Natural gas is a naturally occurring hydrocarbon gas mixture consisting primarily of methane, with other hydrocarbons, carbon dioxide, nitrogen and hydrogen sulfide. It is found in deep underground natural rock formations or associated with other hydrocarbon reservoirs in coal beds and as methane clathrates. Petroleum is also another resource found in proximity to and with natural gas.

Q19. Domestic cooking gas consists mostly of

(a) methane and ethane
(b) liquified butane and isobutane
(c) hydrogen and acetylene
(d) ethylene and carbon monoxide
Ans: (b) Domestic gas is another name for Liquefied Petroleum Gas (LPG). Varieties of LPG bought and sold include mixes that are primarily propane (C3H8), primarily butane (C4H10) and, most commonly, mixes including both propane and butane, depending on the season — in winter more propane, in summer more butane.

Q20. Chemically ‘Quick Silver is known as

(a) Mercury (b) Silver
(c) Gold (d) Copper
Ans: (a) Quicksilver is an alternative name for the element mercury. A heavy, silvery d-block element, mercury is the only metal that is liquid at standard conditions for temperature and pressure; the only other element that is liquid under these conditions is bromine, though metals such as caesium, gallium, and rubidium melt just above room temperature.

Q21. Extensively used nitrogenous fertilizer is

(a) Ammonium nitrate
(b) Urea
(c) Ammonium sulphate
(d) Nitro-lime
Ans: (b) More than 90% of world production of urea is destined for use as a nitrogen-release fertilizer. Urea has the highest nitrogen content of all solid nitrogenous fertilizers in common use. Therefore, it has the lowest transportation costs per unit of nitrogen nutrient.

Q22. The metal, used to galvanise iron to protect it from rusting is

(a) Zinc (b) Chromium
(c) Lead (d) Antimony
Ans: (a) Galvanization is the process of applying a protective zinc coating to steel or iron, in order to prevent rusting. Although galvanization can be done with electrochemical and electro-deposition processes, the most common method in current use is hot-dip galvanization, in which steel parts are submerged in a bath of molten zinc.

Q23. Which of the following gases is mixed with oxygen for breathing by divers in aqualungs?

(a) Methane (b) Nitrogen
(c) Helium (d) Hydrogen
Ans: (b) For some diving, gas mixtures other than normal atmospheric air (21% oxygen, 78% nitrogen, 1% trace gases) can be used, so long as the diver is properly trained in their use. The most commonly used mixture is Nitrox, also referred to as Enriched Air Nitrox (EAN), which is air with extra oxygen, often with 32% or 36% oxygen, and thus less nitrogen, reducing the likelihood of decompression sickness or allowing longer exposure to the same pressure for equal risk.

Q24. What particles move around the nucleus of an atom and are negatively charged?

(a) Electrons (b) Protons
(c) Positrons (d) Neutrons
Ans: (a) Circling around outside the nucleus are tiny little particles called electrons. Electrons have a negative charge. Electrons spin as they circle the nucleus billions of times every second. They are arranged in energy levels around the nucleus. When electrons gain or lose energy, they jump between energy levels as they are rotating around the nucleus.

Q25. Among the following, which is always found in free-state in nature?

(a) Gold (b) Silver
(c) Sodium (d) Copper
Ans: (a) Gold is the least reactive in the reactivity series. Since it does not react with other elements, it is found in a free form. Only gold, silver, copper and the platinum metals occur in nature in larger amounts. Non-metallic elements occurring in the native state include carbon and sulfur.

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