31. In the extraction of iron, carbon acts as:
- A) Oxidizing agent
- B) Reducing agent
- C) Flux
- D) Neutralizer
Answer: B) Reducing agent
Explanation: Carbon, in the form of coke, acts as a reducing agent in the blast furnace. It reduces iron oxide to iron: Fe2O3+3C→2Fe+3CO2
32. The slag formed during the extraction of iron in a blast furnace is:
- A) Ferrous oxide
- B) Calcium silicate
- C) Ferric oxide
- D) Iron silicate
Answer: B) Calcium silicate
Explanation: The slag in the blast furnace is calcium silicate (CaSiO3), formed by the reaction of calcium oxide (from limestone) with silica.
33. In the extraction of iron from haematite, the charge used in the blast furnace consists of:
- A) Haematite, coke, and limestone
- B) Magnetite, coke, and sand
- C) Iron scrap and limestone
- D) Iron oxide and aluminium
Answer: A) Haematite, coke, and limestone
Explanation: The charge in a blast furnace includes haematite (Fe2O3), coke (carbon source), and limestone (flux) to extract iron.
34. The copper obtained from copper pyrites is known as:
- A) Blister copper
- B) Matte
- C) Pure copper
- D) Copper oxide
Answer: A) Blister copper
Explanation: Blister copper is the form of copper obtained after smelting copper pyrites. It contains impurities and has a blistered appearance due to escaping sulfur dioxide gas.
35. The compound of iron which is most suitable for extraction of iron is:
- A) Ferric chloride
- B) Ferrous sulphate
- C) Haematite
- D) Iron pyrite
Answer: C) Haematite
Explanation: Haematite (Fe2O3) is the most suitable ore for the extraction of iron. It is the principal source of iron in the blast furnace process.
36. Which of the following metals is purified by distillation?
- A) Aluminium
- B) Copper
- C) Zinc
- D) Iron
Answer: C) Zinc
Explanation: Zinc has a relatively low boiling point compared to other metals. It can be purified by distillation after smelting.
37. Which of the following is not true for roasting?
- A) Roasting involves heating the ore in the presence of air
- B) Sulphide ores are generally roasted
- C) Roasting converts sulphide ores to oxides
- D) Roasting is used for carbonate ores
Answer: D) Roasting is used for carbonate ores
Explanation: Roasting is generally used for sulphide ores, not carbonate ores. Carbonate ores are typically subjected to calcination.
38. In the extraction of copper, which material is added to remove the impurity of iron?
- A) Lime
- B) Coke
- C) Silica
- D) Charcoal
Answer: C) Silica
Explanation: Silica is added to remove the impurity of iron in the form of iron silicate (slag) during copper extraction.
39. In the metallurgy of iron, limestone is added to the furnace to:
- A) Reduce iron oxide to iron
- B) Act as a flux
- C) Act as an oxidizing agent
- D) Remove impurities
Answer: B) Act as a flux
Explanation: Limestone acts as a flux in the blast furnace, which combines with impurities to form slag (calcium silicate).
40. Which of the following is not used as a flux in metallurgy?
- A) Silica
- B) Lime
- C) Cryolite
- D) Coke
Answer: D) Coke
Explanation: Coke is a reducing agent, not a flux. Fluxes like silica, lime, and cryolite are used to remove impurities.
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