Chemistry (Part-II) (UPSC)

Total Questions: 56

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

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.
Regulation of Methanol in India
• Schedule I of the Manufacture, Storage and Import of Hazardous Chemical Rules 1989 includes methanol.
• The Food Safety and Standards (Alcoholic Beverages) Regulations 2018 stipulate the maximum permissible quantity of methanol in different liquors.
• For example, these values span a wide range including “absent” in coconut fenny, 50 grams per 100 litres in country liquor, etc.
• The Indian Standard (IS 517) applies to how the quality of methanol is to be ascertained, and together with the Tamil Nadu Denatured Spirit, Methyl Alcohol, and Varnish (French Polish) Rules 1959, what signage, methanol packaging should carry.

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

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.
• Garlic is a good source of several nutrients and bioactive compounds, including;
• Vitamins: Vitamin C, Vitamin B6.
• Minerals: Manganese, Selenium, Calcium, Copper, Potassium.
• Fiber: Garlic contains a small amount of dietary fiber.
• Antioxidants: Allicin (a sulfur compound that provides many of garlic's health benefits).
• Additionally, garlic has been associated with various health benefits, such as improving heart health, boosting the immune system, and possessing anti-inflammatory and antimicrobial properties.

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

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]

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.
  • Skin contact with sulphur mustard liquid or vapour causes redness and blisters. The effects on the skin may be delayed for several hours. It can also affect the eyes causing tearing, irritation, burning, redness and swelling of the eyelids. This may progress causing sensitivity to light and possibly blindness.
  • Inhalation of sulphur mustard vapour causes hoarseness, cough and pain on coughing. In severe cases permanent lung damage may occur, fluid may build up on the lungs, a condition known as pulmonary oedema (pronounced ‘ed-eem-a’) and exposure may also increase an individual’s chance of developing future respiratory tract infections.
  • Ingestion of sulphur mustard may induce nausea, vomiting, vomiting blood, abdominal pain, and diarrhoea, and in severe cases heart problems, may occur within a few hours.
  • Most individuals who suffer from mild short-term symptoms recover completely. However, some severely affected individuals may develop eye, skin and breathing problems and may suffer from long term-tiredness, which can take some time to clear.

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

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]

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.

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.
• Phenyl is toxic; accidental ingestion or contamination (like in food) is dangerous, affecting CNS, heart, liver, kidneys, and requires immediate medical attention.
• Manufacturing: Made from rosin, castor oil, and caustic soda (NaOH), involving saponification.

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.

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.

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.
  • Formic acid is a colorless liquid having a highly pungent, penetrating odor at room temperature.
  • It is miscible with water and most polar organic solvents and is somewhat soluble in hydrocarbons.
  • In hydrocarbon and in the vapor phase, it contains hydrogen-bonded dimers rather than individual molecules.
  • Solid formic acid consists of an effectively endless network of hydrogen-bonded formic acid molecules.
  • Formic acid is corrosive to metals and organic tissues. Since it is a simple form of carboxylic acid, it occurs in the form of acetic acids and amino acids and is the main ingredient in vinegar.

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. Cracking1. Rubber
B. Smelting2. Petroleum
C. Hydrogenation3. Copper
D. Vulcanization4. Edible fats

Codes:

ABCD
(a)3214
(b)2341
(c)2314
(d)3241
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.