Microtheme: Chemistry —
15 questions asked in Prelims in the past.

1. [2025] Consider the following:
   I. Cigarette butts
   II. Eyeglass lenses
   III. Car tyres
   How many of them contain plastic?
   • (a) Only one
   • (b) Only two
   • (c) All the three
   • (d) None
   Correct Answer: (C) All the three
2. [2021] Water can dissolve more substances than any other
   liquid because
   • (a) it is dipolar in nature
   • (b) it is a good conductor of heat
   • (c) it has high value of
   • (d) it is an oxide of hydrogen
   Correct Answer: (A) it is dipolar in nature
3. [2014] 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 only
   • (d) None of the above
   Correct Answer: (B) 3 only
4. [2013] Fruits stored in a cold chamber exhibit longer storage life because
   • (a) exposure to sunlight is prevented
   • (b) concentration of carbon dioxide in the environment is increased
   • (c) rate of respiration is decreased
   • (d) there is an increase in humidity
   Correct Answer: (C) rate of respiration is decreased
5. [2011] Aspartame is an artificial sweetener sold in the market. It consists of amino acids and provides calories like other amino acids. Yet, it is used as a low-calorie sweetening agent in food items. What is the basis of this use?
   • (a) Aspartame is as sweet as table sugar, but unlike table sugar, it is not readily oxidized in the human body due to lack of requisite enzymes.
   • (b) When aspartame is used in food processing, the sweet taste remains, but it becomes resistant to oxidation.
   • (c) Aspartame is as sweet as sugar, but after ingestion into the body, it is converted into metabolites that yield no calories.
   • (d) Aspartame is several times sweeter than table sugar, hence food items made with small quantities of aspartame yield fewer calories on oxidation.
   Correct Answer: (D) Aspartame is several times sweeter than table sugar, hence food items made with small quantities of aspartame yield fewer calories on oxidation.
6. [2010] Indiscriminate disposal of used fluorescent electric lamps causes mercury pollution in the environment. Why is mercury used in the manufacture of these lamps ?
   • (a) A mercury coating on the inside of the lamp makes the light bright white
   • (b) When the lamp is switched on, the mercury in the lamp causes the emission of ultra-violet radiations
   • (c) When the lamp is switched on, it is the mercury which converts the ultra-violet energy into visible light
   • (d) None of the statement given above is correct about the use of mercury in the manufacture of fluorescent lamps
   Correct Answer: (B) When the lamp is switched on, the mercury in the lamp causes the emission of ultra-violet radiations
7. [2010] 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
   Correct Answer: (B) the formation of hypochlorous acid when chlorine is added to water
8. [2010] If a potato is placed on a pure paper plate which is white and unprinted and put in a microwave oven, the potato heats up but the paper plate does not. This is because:
   • (a) Potato is mainly made up of starch whereas paper is mainly made up of cellulose
   • (b) Potato transmits microwaves whereas paper reflects microwaves
   • (c) Potato contains water whereas paper does not contain water
   • (d) Potato is a fresh organic material whereas paper is a dead organic material.
   Correct Answer: (C) Potato contains water whereas paper does not contain water
9. [2009] Which one of the following is used as an explosive ?
   • (a) Phosphorous Trichloride
   • (b) Mercuric Oxide
   • (c) Graphite
   • (d) Nitroglycerine
   Correct Answer: (D) Nitroglycerine
10. [2008] What are rubies and sapphires chemically known as?
    • (a) Silicon dioxide
    • (b) Aluminum oxide
    • (c) Lead tetroxide
    • (d) Boron nitride
    Correct Answer: (B) Aluminum oxide
11. [2008] Which one of the following is also called Stranger Gas?
    • (a) Argon
    • (b) Neon
    • (c) Xenon
    • (d) Nitrous oxide
    Correct Answer: (C) Xenon
12. [2008] 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
    Correct Answer: (C) Methane and air
13. [2008] 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) Aluminum and osmium
    • (d) Aluminum and mercury
    Correct Answer: (B) Lithium and osmium
14. [2008] What is the pH level of blood of a normal person?
    • (a) 4.5-4.5
    • (b) 6.45-6.55
    • (c) 7.35-7.45
    • (d) 8.25-8.35
    Correct Answer: (C) 7.35-7.45
15. [2003] Regarding the atom of a chemical element, the magnetic quantum number refers to:
    • (a) Orientation
    • (b) Shape
    • (c) Size
    • (d) Spin
    Correct Answer: (A) Orientation