Chemistry (Part-II) (UPSC)

Total Questions: 28

21. Which one of the following is the correct sequence in increasing order of molecular weights of the hydrocarbons? [2001]

(a) Methane, ethane, propane and butane
(b) Propane, butane, ethane and methane
(c) Butane, ethane, propane and methane
(d) Butane, propane, ethane and methane

Correct Answer: (a) Methane, ethane, propane and butane

Solution:As molecular weight increases with increase in the length of carbon-carbon chain.

22. The purpose of adding sodium sulphate and sodium silicate to the detergent in a washing powder is : [2003]

1. to keep the washing powder dry.

2. to maintain the alkalinity of the powder.

Which of these statements is/are correct?

(a) only 1
(b) Only 2
(c) Both 1 and 2.
(d) Neither 1 nor 2

Correct Answer: (c) Both 1 and 2.

Solution:Sodium sulphate helps to keep the detergent dry and free-flowing, while sodium silicate helps to maintain the alkalinity of the powder. This alkalinity is necessary to break down dirt and grease, and to help the detergent to dissolve in water. Without sodium sulphate, the detergent would be more likely to clump together and become difficult to use. Without sodium silicate, the detergent would be less effective at cleaning clothes. Thus the correct answer is (c).

23. Match List-I (Fuel gases) with List-II (Major constituents) and select the correct answer using the codes given below the lists [2004]

List-I	List-II
A. CNG	1. Carbon monoxide, Hydrogen
B. Coal gas	2. Butane, Propane
C. LPG	3. Methane, Ethane
D. Water gas	4. Hydrogen, Methane, Carbon monoxide

Codes:

	A	B	C	D
(a)	2	1	3	4
(b)	3	4	2	1
(c)	2	4	3	1
(d)	3	1	2	4

Correct Answer: (b)

Solution:Compressed natural gas (CNG) is made by compressing natural gas which is composed of methane (CH), it also contain small amount of ethane.

Coal gas typically contains hydrogen, methane and carbon monoxide.

LPG is the abbreviation or short form of Liquefied Petroleum gas. The major constituents of LPG is propane and butane.

Water gas is a synthesis gas, containing carbon monoxide and hydrogen.

24. Consider the following statements: [2005]

1. Liquefied natural gas (LNG) is liquefied under extremely cold temperatures and high pressure to facilitate storage or transportation in specially designed vessels.

2. First LNG terminal in India was built in Hassan.

3. Natural gas liquids (NGL) are separated from LPG and these include ethane, propane, butane and natural gasoline.

Which of the statements given above is/are correct?

(a) 1 only
(b) 1 and 3
(c) 2 and 3
(d) 1, 2, and 3

Correct Answer: (b) 1 and 3

Solution:Liquified Natural Gas or LNG is natural gas (predominantly methane, CH) that has been converted temporarily to liquid form for ease of storage or transport. The liquefaction process involves removal of certain components, such as dust, acid gases, helium, water, and heavy hydrocarbons, which could cause difficulty downstream. The natural gas is then condensed into a liquid maximum transport pressure set at around 25 kPa/3.6 psi by cooling it to approximately 162 °C (-260 °F). Dahej, in India has begun its first import of natural gas. Natural gas liquids recovery (NGL) involves refrigerated gas plants, turboexpanders, debutanizers, depropanizers, and JT plants. NGL can be separated using debutanizers and depropanizers into propane, butane, naphtha, etc.

25. 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: [2005]

Assertion (A): The main constituent of the liquefied petroleum gas is methane.

Reason (R): Methane can be used directly for burning in homes and factories where it can be supplied through pipelines.

(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: (d) A is false but R is true

Solution:Varieties of LPG bought and sold include mixes that are primarily propane and butane, the common, mixes include propane (60%) and butane (40%), depending on the season in winter more propane, in summer more butane. Propylene and butylenes are usually also present in small concentration. A powerful odorant, ethanethiol, is added so that leaks can be detected easily.

Methane is a chemical compound with the chemical formula (CH). Compared to other hydrocarbon fuels, burning methane produces less carbon dioxide for each unit of heat released. In many cities, methane is piped into homes for domestic heating and cooking purposes.

Methane in the form of compressed natural gas is used as a vehicle fuel. Methane is used in industrial chemical processes for the production of hydrogen, methanol, acetic acid, and acetic anhydride, also used as a fuel in factories.

26. Consider the following chemicals: [2006]

1. Benzene

2. Carbon tetrachloride

3. Sodium carbonate

4. Trichloroethylene

Which of the above/is are used as dry cleaning chemical?

(a) 1 only
(b) 2 only
(c) 1, 2 and 4 only
(d) 1, 2, 3 and 4

Correct Answer: (c) 1, 2 and 4 only

Solution:Dry cleaning is a cleaning process for clothing and textiles involves using a chemical solvents other then water. The solvent used is typically trichloroethylene while carbon tetra chloride and tri chloroethane is used historically. Benzene is other common agent used for this purpose.

The best eco friendly cleaning used these days is hydrogen peroxide. The use of hydrogen peroxide gives better results for the purpose of bleaching clothes in laundry. Secondly it also helps in less consumption of water.

27. Which one of the following is another name of RDX? [2007]

(a) Cyanohydrin
(b) Dextran
(c) Cyclohexane
(d) Cyclonite

Correct Answer: (d) Cyclonite

Solution:RDX, an initialism for Research Department Explosive, is an explosive nitroamine widely used in military and industrial applications. It is also known less commonly as cyclonite. Its chemical name is cyclotrimethylene trinitramine.

28. What is Bisphenol A (BPA)? [2008]

(a) A medical test for detecting cancer
(b) A test for testing the use of drugs to improve performance by athletes
(c) A chemical used for the development of food packaging materials
(d) A special type of alloy steel

Correct Answer: (c) A chemical used for the development of food packaging materials

Solution:Bisphenol A, commonly abbreviated as BPA, is an organic compound with two phenol functional groups. Bisphenol A is used primarily to make plastics which is used in making food packaging material. It is a key monomer in production of epoxy resins and used to make polycarbonate plastic.

Polycarbonate plastic, which is clear and nearly shatter-proof, is used to make a variety of common products including baby and water bottles, sports equipment, medical and dental devices, dental fillings and sealants, eyeglass lenses, CDs and DVDs, and household electronics.

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