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Part 047 – Chemistry Previous Year Questions

Q1. The fiber least prone to catch fire is
(a) nylon (b) polyester
(c) cotton (d) terylene
Ans: (c) The fiber least prone to catch fire is cotton. Besides, in cases of fire due to electricity, cotton is less prone to static electricity buildup than nylon or other synthetics. Cotton and wool are naturally less prone to burning because the fire can be smothered in the thick fibers.

Q2. Setting of plaster of paris involves

(a) dehydration process
(b) hydration to form other hydrates
(c) oxidation process
(d) reduction process
Ans: 2. (b) The setting of plaster of Paris takes place by hydration due to the formation of a solid crystalline hydrate and hardening of Plaster of Paris is hydration reaction, which is reverse of the dehydration of gypsum. Plaster of Paris quickly sets to a hard mass when made into a thin paste with water. A slight expansion takes place in the process and heat is evolved. This process is exothermic.

Q3. The common name for the compound having formal NaOH is

(a) Caustic soda
(b) Caustic potash
(c) Soda ash
(d) Sodium hydroxide
Ans: (a) Sodium hydroxide, also known as lye or caustic soda, has the molecular formula NaOH and is a highly caustic metallic base. It is a white solid available in pellets, flakes, granules, and as a 50% saturated solution. It is used in many industries, mostly as a strong chemical base in the manufacture of pulp and paper, textiles, drinking water, soaps and detergents and as a drain cleaner.

Q4. Which one of the following is found in kidney stones?

(a) Sodium oxalate
(b) Calcium oxalate
(c) Sodium chloride
(d) Calcium acetate
Ans: (b) Calcium is one component of the most common type of human kidney stones, calcium oxalate. Some studies suggest people who take supplemental calcium have a higher risk of developing kidney stones, and these findings have been used as the basis for setting the recommended daily intake for calcium in adults.

Q5. Bone ash contains

(a) Calcium sulphate
(b) Phosphoric sulphate
(c) Calcium phosphate
(d) Calcium hypophosphate
Ans: (c) Bone ash is a white material produced by the calcination of bones. It is primarily composed of calcium phosphate. It is commonly used in fertilizers, polishing compounds and in making ceramics such as bone china. It also has historical uses in the manufacture of baking powders and assay cupels.

Q6. Helium gas is filled in ballons because

(a) its atomic number is 2
(b) it is lighter than air
(c) it is one of the constitutents of water
(d) it is a noble gas
Ans: (b) Helium is the second lightest element and is the second most abundant element in the observable universe, being present at about 24% of the total elemental mass, which is more than 12 times the mass of all the heavier elements combined. A wellknown but minor use is as a lifting gas in balloons and airships

Q7. The ratio of pure gold in 18 carat gold is

(a) 100% (b) 80%
(c) 75% (d) 60%
Ans: (c) The gold content of alloys is measured in carats (k). Pure gold is designated as 24k where the ratio of pure gold is supposed to be 100 per cent. So 18 k gold will have pure gold ratio of 75 per cent.

Q8. Acid secretion is characteristic of

(a) Buccal cavity
(b) Stomach
(c) Small intestine
(d) Large intestine
Ans: (b) The stomach is famous for its secretion of hydrochloric acid. It is secreted from parietal cells into the lumen where it establishes an extremely acidic environment. This acid is important for activation of pepsinogen and inactivation of ingested microorganisms such as bacteria.

Q9. Which one of the following is not a fertilizer?

(a) Ammonium sulphate
(b) Calcium sulphate
(c) Calcium ammonium nitrate
(d) Potassium nitrate
Ans: (b) Calcium sulfate is a common laboratory and industrial chemical. In the form of -anhydrite (the nearly anhydrous form), it is used as a desiccant. It is also used as a coagulant in products like tofu. The main sources of calcium sulfate are naturally occurring gypsum and anhydrite which occur at many locations worldwide as evaporites.

Q10. Slag is a name given for

(a) molten iron
(b) molten sand
(c) molten alumina
(d) molten calcium silicate
Ans: (c) Slag is a partially vitreous by-product of the process of smelting ore, which separates the desired metal fraction from the unwanted fraction. A good example is steelmaking slag: quicklime and magnesite are introduced for refractory protection, neutralizing the alumina and silica separated from the metal, and assist in the removal of sulfur and phosphorus from the steel.

Q11. Which one of the following statements is not correct?
Vulcanisation of rubber makes it

(a) soft and flexible
(b) strong and hard
(c) chemical resistant
(d) withstand higher temperatures
Ans: (a) In order to give more strength and more elasticity, natural rubber is heated with sulphur or sulphur compounds at 150°C temperature. Vulcanized rubber has good tensile strength. The working temperature of vulcanized rubber is enhanced up to 100°C. It has good resistance to organic solvents.

Q12. Stainless steel is usually made by alloying the steel with

(a) copper and nickel
(b) copper and chromium
(c) chromium and nickel
(d) manganese and copper
Ans: (c) In metallurgy, stainless steel is defined as a steel alloy with a minimum of 10.5 per cent to 11 per cent chromium content by mass. There are different types of stainless steels: when nickel is added, for instance, the austenite structure of iron is stabilized. This crystal structure makes such steels virtually non-magnetic and less brittle at low temperatures. For greater hardness and strength, more carbon is added.

Q13. Which one of the following organic compound is used to remove stains of iron compounds?

(a) Oxalic acid
(b) Benzoic acid
(c) Phthalic acid
(d) Cinnamic acid
Ans: (a) Oxalic acid is a reducing agent and its conjugate base, known as oxalate (C2O4 2–), is a chelating agent for metal cations. Oxalic acid’s main applications include cleaning or bleaching, especially for the removal of rust, e.g. Bar Keepers Friend is an example of a household cleaner containing oxalic acid. Its utility in rust removal agents is due to its forming a stable, water soluble salt with ferric iron, ferrioxalate ion.

Q14. Which one of the following is used as a sowing agent in the preparation of soft drinks?

(a) Phosphoric acid
(b) Phosphorus acid
(c) Salicylic acid
(d) Boric acid
Ans: (a) Phosphoric acid was the foundation of the softdrink industry, long before Coca-Cola’s popularity. Phosphoric acid is deliberately added to soft drinks to give them a sharper flavor. It also slows the growth of molds and bacteria, which would otherwise multiply.

Q15. The coating of a thin layer of zinc on steel or iron objects is known as

(a) Hot dipping
(b) Tinning
(c) Galvanising
(d) Electroplating
Ans: (c) 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.

Q16. Which one of the following gases has the highest calorific value?

(a) Natural gas (b)Water gas
(c) Coal gas (d) Indane gas
Ans: (d) The basic calorific value for solid and liquid fuels is the gross calorific value at constant volume and for gaseous fuels it is the gross calorific value at constant pressure. The calorific value in Kcal/Kg: Coal: 4000- 7000; Natural gas: 8600; Coal gas: 4000; Water gas: 4600-4800; and LPG (liquefied petroleum gas such as Indane): 11,900 Kcal/Kg.

Q17. Which type of radiations are absorbed by the upper layer of the atmosphere?

(a) Radio-waves (b) Infrared
(c) Visible (d) Ultraviolet
Ans: (d) The Troposphere is the layer where the weather happens. Above this layer is the Stratosphere and in between them is the Ozone layer that absorbs the sun’s harmful ultraviolet rays. Above the Stratosphere is the Mesosphere, the Thermosphere including the Ionosphere – and the Exosphere.

Q18. An example of replenshible energy source is—

(a) Coal (b) Petroleum
(c) Lignite (d) Biomass
Ans: (d) Biomass is biological material from living, or recently living organisms, most often referring to plants or plant-derived materials. As a renewable energy source, biomass can either be used directly, or indirectly — once or converted into another type of energy product such as biofuel. Biomass can be converted to energy in three ways: thermal conversion, chemical conversion, and biochemical conversion.

Q19. Which one of the following minerals is found in pure form?

(a) Iron (b) Copper
(c) Bauxite (d) Manganese
Ans: (b) Copper is one of very few elements that are found in essentially pure form in nature. But the bulk of the copper resource is found in other minerals.

Q20. Tar roads get damaged if there is

(a) stagnation of water on road
(b) heavy traffic
(c) no maintenance
(d) no sloping
Ans: (a) Overflow of water or water stagnation damage tar roads. Water which penetrates the surface can get into the base course to cause trouble, and at the same time start oxidizing the binder inside the pavement.

Q21. The drug ‘Marijuana’ is a

(a) sedative
(b) mental stimulant
(c) hallucinating substance
(d) tranquillizer
Ans: (a) Cannabis, also known as marijuana is a preparation of the Cannabis plant intended for use as a psychoactive drug and as medicine. Cannabis indica is known for sedative effects and preferred night time as medical cannabis.

Q22. The material known in commerce as Terylene is a

(a) Synthetic fibre
(b) Natural fibre
(c) Modified natural fibre
(d) Blend of cotton and silk
Ans: (a) Terylene is the name for a synthetic polyester fibre. It is a synthetic polyester fibre or fabric based on terephthalic acid, characterized by lightness and crease resistance and used for clothing, sheets, ropes, sails, etc.

Q23. Among the fuels given below, the one with highest calorific value is

(a) Coke (b) Coal
(c) Wood (d) Natural gas
Ans: (d) The calorific values of different fuels (in Kcal/kg) in dry state are: Wood: 3500; Coal: 4000-7000; Coke: 6500; and Natural Gas: 8600 Kcal/kg.

Q24. The chemical used in embalming biological materials is

(a) formaldehyde in water
(b) formaldehyde in methanol
(c) ethylene glycol
(d) gaseous formaldehyde
Ans: (a) Embalming fluids use formaldehyde as a preservative. Formaldehyde is the simplest aldehyde with the chemical formula HCHO. Formalin is a solution of formaldehyde in water, usually with a small amount of methanol added. Modern formaldehyde based embalming fluids are much kinder to the environment than those used in previous years.

Q25. Which of the following is a monoatomic gas?

(a) Oxygen (b) Neon
(c) Nitrogen (d) Fluorine
Ans: (b) All elements will be monatomic in the gas phase at sufficiently high temperatures. At standard temperature and pressure (STP), all of the noble gases are monatomic. These are helium, neon, argon, krypton, xenon and radon. Monatomic hydrogen comprises about 75% of the elemental mass of the universe.

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