Chemistry (Part-I) (UPSC)

Total Questions: 50

31. Consider the following statements: [1998]

Coke is one of the materials of the charge added to blast furnace for the production of steel/iron. Its function is to :

1. act as the reducing agent.
2. remove silica associated with the iron ore.
3. function as fuel; to supply heat.
4. act as an oxidizing agent.

Correct Answer: (c) 1 and 3 are correct
Solution:This statement 1 is correct. Coke primarily consists of carbon, which reacts with the oxygen in the iron ore (hematite, Fe₂O₃) to reduce it to iron. The carbon in coke forms carbon monoxide (CO) which is a strong reducing agent that reduces iron oxides to iron.
Chemical equations involved in process are following:

2C(s) + O2(g)→ 2CO(g)
FeO(s) + CO(g) → Fe(s) + CO₂(g)
Fe₂O₃ +3CO(g)→ 2Fe(s) + 3CO₂(g)

The removal of silica (SiO₂) is typically achieved by adding limestone (CaCO₃), not coke. The limestone decomposes to form calcium oxide (CaO), which then reacts with silica to form calcium silicate (slag). Thus statement 2 is not correct This statement 3 is correct. Coke serves as a fuel to generate the high temperatures required in the blast furnace. The combustion of coke provides the necessary heat for the reduction reactions and the melting of iron.

Thus, the correct statements are 1 and 3.

32. Which one of the following metals does not form amalgam? [1998]

Correct Answer: (d) Iron
Solution:Amalgam is an alloy consisting of mercury and any other element. Iron being exceptional in nature not form amalgam with mercury. That's why mercury is stored in vessels made up of iron. Small quantities of an iron amalgam have, however, been formed by immersing sodium amalgam (containing 1 percent sodium) in a clear, saturated solution of ferrous sulphate. While rest three options zinc,copper and magnesium combine with mercury to form there respective amalgam.

33. (Questions 33-34) The following two Items consist statements. One labeled as the 'Assertion (A)' and the other as "Reason (R). You have to answer these items using the code given below: [1998]

Assertion (A): Sodium metal is stored under kerosene.
Reason (R): Metallic sodium melts when exposed to air.

Correct Answer: (c) A is true but R is false
Solution:Sodium metal is generally kept inside kerosene oil because of its extreme reactive nature. In open air it reacts violently and burns vigorously to form sodium oxide.

The presence of sodium ions in a salt can be determined by the color of a flame-Na turns flame yellow.

34. You have to answer these items using the code given below: [1999]

Assertion (A): To dilute sulphuric acid, acid is added to water and not water to acid.
Reason (R): Specific heat of water is quite large.

Correct Answer: (a) Both A and R are true and R is the correct explanation of A
Solution:Sulphuric acid (H₂SO₄) reacts very vigorously with water. in a highly exothermic reaction. Thus if you add water to concentrated sulfuric acid, it can boil and you may get a nasty acid burn. That's why for dilution, acid is added to water not water to acid as specific heat of water is quite large and it can absorb large quantity of heat produced by sulphuric acid Moreover water is less dense than sulphuric acid, so if you pour water on the acid, the reaction occurs on top of the liquid. If you add the acid to the water, it sinks and any wild and crazy reactions have to get through the water or beaker to get to you.

35. Match List-I (Naturally occurring substances) with List-II (Elements) and select the correct answer using the codes given the lists: [1999]

List-IList-II 
A Diamond1. Calcium
B. Marble2. Silicon
C. Sand3. Aluminium
D. Ruby4. Carbon

 

Code:ABCD
(a)3124
(b)4213
(c)2134
(d)4123
Correct Answer: (d)
Solution:Diamonds is the polymorph of the element carbon. Calcium is the basic element of naturally occuring marble. Sand is formed by Silicon and Aluminium is the basic element of naturally occuring Ruby (Al₂O₂)

36. Match List-I with List-II and select the correct answer using the codes given below the lists: [2000]

List-IList-II 
A. German silver1. Tin
B. Solder2. Nickel
C. Bleaching powder3. Sodium
D. Hypo4. Chlorine

 

Code:ABCD
(a)1243
(b)2134
(c)1234
(d)2143
Correct Answer: (d)
Solution:German silver has a color resembling silver, but is an alloy of primarily copper, nickel and zinc.
Solder is an alloy of tin, antimony, copper and lead. Bleaching powder contains calcium chloride and calcium hypochlorite, used in solution as a bleach. Bleaching powder is sold on the basis of available chlorine, which is liberated when it is treated with a dilute acid. It is used for bleaching paper pulps and fabrics and for sterilizing water.
Hypo solution used in iodometric titration is sodium thiosulphate (Na₂S₂O₃).

37. Which one of the following materials is very hard and very ductile? [2000]

Correct Answer: (d) Nichrome
Solution:Nichrome is a non-magnetic alloy of nickel, chromium, and iron, usually used as a resistance wire. A common alloy is 80% nickel and 20% chromium, by mass. This alloying provide nichrome properties like hardness and ductility.
• Nichrome is an alloy of Manganese 1.5%, Nickel 75% to 78%, Chromium 20% to 23%, and a little percentage of iron.
• Nichrome has high resistivity. Nichrome is a non-magnetic alloy that is made up of mainly chromium and nickel.
• It has a very high melting point, which makes it nichrome to make high-temperature wires.
• It is used in heating elements such as hair dryers, toasters, and ovens.
• Nichrome is used to make the coils used in water heaters.

38. Aluminium surface are often 'anodized'. This means the deposition of a layer of [2000]

Correct Answer: (b) aluminium oxide
Solution:Anodizing or anodising in British English, is an electrolytic passivation process used to increase the thickness of the natural oxide layer on the surface of metal parts. The process is called "anodizing" because the part to be treated forms the anode electrode of an electrical circuit. Anodizing increases corrosion and wear resistance. The anodized aluminium layer is grown by passing a direct current through an electrolytic solution, with the aluminium object serving at the anode. The current releases hydrogen at the cathode and oxygen at the surface of the aluminium anode, creating a build up of aluminium oxide layer.

39. Consider the following statements: Hard water is not suitable for [2000]

1. drinking
2. washing clothes with soap
3. use in boilers
4. irrigating crops

Which of these statements are correct?

Correct Answer: (d) 1, 2, 3 and 4
Solution:Hardness of water is due to presence of chlorides, sulphates and nitrates of calcium and magnesium. Hard water cannot be used for washing purposes as soap do not form lather with hard water easily which results in to wastage of soap in laundaries. Moreover use of hard water in industries results in to scale formation in inner layers of boilers on which insoluble calcium and magnesium carbonates gets deposited and being a bad conductor of heat result in to wastage of energy. Moreover hard water is not fit for drinking purpose as it hinders ionic imbalance in body. Repeated irrigation of crops by hard water increases calcium and magnesium ions in soil which increases soil alkalinity.

40. An aqueous solution of copper sulphate is acidic in nature because the salt undergoes [2001]

Correct Answer: (c) hydrolysis
Solution:Aqueous solution of copper sulphate is acidic in nature because copper sulphate on dissolving with water, following chemical reaction takes place
CuSO₄(s) + 2H₂O → Cu(OH)₂(l) + H₂SO₄(aq)
Now as we can see in above chemical equation the sulphuric acid generated is strong mineral acid which results into increase in acidity of solution. Thus aqueous solution of copper sulphate is acidic in nature.