Chemistry (Part-II) (UPSC)

Total Questions: 28

11. The offending substance in the liquor tragedies leading to blindness etc. is [1996]

(a) ethyl alcohol
(b) amyl alcohol
(c) benzyl alcohol
(d) methyl alcohol

Correct Answer: (d) methyl alcohol

Solution:Methyl alcohol is very dangerous. May be fatal or cause blindness if swallowed. Harmful, if inhaled or absorbed through skin. It cannot be made non poisonous. Some other harmful effects are results into irritation of skin, eyes and respiratory track. It can also effects central nervous system and liver.

12. The characteristic odour of garlic is due to : [1997]

(a) a chloro compound
(b) a sulphur compound
(c) a fluorine compound
(d) acetic acid

Correct Answer: (b) a sulphur compound

Solution:Allicin is an oily, yellow liquid, which gives garlic its characteristic odour which is due to the R-S(O)-S-R group. It also has a range of medical properties.

13. Which one of the following is an active component of oil of clove? [1997]

(a) Menthol
(b) Eugenol
(c) Methanol
(d) Benzaldehyde

Correct Answer: (b) Eugenol

Solution:Oil of cloves, also known as Clove oil, is an essential oil obtained from the clove plant. It is a natural analgesic and antiseptic used primarily in dentistry for its main ingredient eugenol.

The oil produced by cloves can be used in many things from flavouring medicine to remedies for bronchitis, common cold, a cough, fever, sore throat and tending to infections.

14. Which one of the following was used as a chemical weapon in the first world war? [1997]

(a) Carbon monoxide
(b) Hydrogen cyanide
(c) Mustard gas
(d) Water gas

Correct Answer: (c) Mustard gas

Solution:The most effective gas of the first world war was mustard gas a vesicent, which was introduced by Germany in July 1917. Mustard gas is not a particularly effective killing agent but the skin of its victims got blistered, their eyes became very sore and they began to vomit. Mustard gas caused internal and external bleeding and attacked the bronchial tubes.

15. Which one of the following has the highest fuel value? [1997]

(a) Hydrogen
(b) Charcoal
(c) Natural gas
(d) Gasoline

Correct Answer: (a) Hydrogen

Solution:Fuel value can be expressed in terms of calorific value of fuel. The calorific value of a fuel is the amount of heat produced by burning 1 kg of fuel. Hydrogen has the highest calorific value of (141,790 KJ/kg) thus have highest fuel value.

Calorific value of charcoal, natural gas and gasoline are (29,600; 43,000; 47,300 kJ/kg) respectively. Natural gas majorly consists of methane.

16. Which one of the following is used as an anti-freeze for the automobile engines? [1997]

(a) Propyl alcohol
(b) Ethanol
(c) Methanol
(d) Ethylene glycol

Correct Answer: (d) Ethylene glycol

Solution:Ethylene glycol solutions are marketed as "permanent anti-freeze", and is used as anti-freeze agent for the automobile engine in cold countries where temperature is below zero degree centigrade.

17. The following item consists of two statements. One labeled as the 'Assertion (A)' and the other as "Reason have to answer this item using the code given below: [1998]

Assertion (A): Phenyl is used as a household germicide.

Reason (R): Phenyl is phenol derivative and phenol is an effective germicide.

(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

Correct Answer: (a) Both A and R are true and R is the correct explanation of A

Solution:Antiseptic are antimicrobial substances that are applied to living tissue/skin to reduce the possibility of infection, sepsis, or putrefaction. Now phenyl being a phenol derivative possesses effective germicidal properties because phenol is germicidal in strong solution.

18. Consider the following statements about acetylene: [1998]

1. It is used in welding industry.

2. It is a raw material for preparing plastics.

3. It is easily obtained by mixing silicon carbide and water of these statements.

(a) 1 and 2 are correct
(b) 1 and 3 are correct
(c) 2 and 3 are correct
(d) 1, 2 and 3 are correct

Correct Answer: (a) 1 and 2 are correct

Solution:Acetylene produces a flame temperature of-3100 degree Celsius along with oxygen. This high flame temperature makes acetylene a suitable choice for gas welding steel. When burned in oxygen, acetylene produces a reducing zone, which easily cleans the metal surface. Today, oxy-acetylene welding is employed for high strength steels. The efficiency of acetylene when used with oxygen is very high. This means that the gasses, especially the oxygen, lasts longer. Thus, this results in less cylinder handling.

It is also used as a raw material for the production of various chemicals such as polyester plastics, polyurethane, and more. Acetylene gas is colorless and odorless when pure. Thus, statement 1 and 2 are correct.

19. The following item consists of two statements. One labeled as the 'Assertion (A)' and the other as "Reason (R). You have to answer this item using the code given below: [1998]

Assertion (A): Formic acid is a stronger acid than acetic acid.

Reason (R): Formic acid is an organic acid.

(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

Correct Answer: (b) Both A and R are true but R is not a correct explanation of A

Solution:Formic acid is stronger than acetic acid due to its chemical composition. Formic acid is an organic acid.

20. Match List-I (Industrial process) with List-II (Industry with which associated) and select the correct answer using the codes given below the lists: [2000]

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

Correct Answer: (b)

Solution:Cracking is the process whereby complex organic molecules such as kerosene or heavy hydrocarbons are broken down into simpler molecules such as light hydrocarbons, by the breaking of carbon-carbon bonds.

Smelting is a form of extractive metallurgy; its main use is to produce a metal from its ore. In this process the oxide ore is reduced to free metal by using reducing agents like coke or charcoal. Copper is also obtained from its oxide by this method in free state.

Hydrogenation is a reduction reaction which results in an addition of hydrogen (usually as H.). If an organic compound is hydrogenated, it becomes more 'saturated". Hydrogenation results in the conversion of liquid vegetable oils to solid (edible) fats.

Vulcanization is a chemical process for converting rubber into more durable materials via the addition of sulphur. Sulphur modify the rubber by forming crosslinks (bridges) between individual polymer chains. Vulcanized material is less sticky and has superior mechanical properties.

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