71. Which of the following is not a part of the blast furnace process for extracting iron?
- A) Roasting
- B) Reduction
- C) Smelting
- D) Calcination
Answer: D) Calcination
Explanation: Calcination is not part of the blast furnace process. It involves heating ores in the absence of air, while the blast furnace involves reduction and smelting.
72. In the extraction of copper from copper pyrites, the matte contains:
- A) Copper sulphide and iron sulphide
- B) Copper oxide and iron oxide
- C) Copper and zinc
- D) Copper oxide and carbon
Answer: A) Copper sulphide and iron sulphide
Explanation: The matte formed in copper extraction consists of copper sulphide (Cu2S) and iron sulphide (FeS).
73. In the blast furnace, which of the following acts as a flux?
- A) Coke
- B) Silica
- C) Calcium oxide
- D) Alumina
Answer: C) Calcium oxide
Explanation: Calcium oxide (lime) is used as a flux in the blast furnace. It reacts with silica impurities to form calcium silicate (slag).
74. The role of cryolite in the electrolytic extraction of aluminium is to:
- A) Increase the electrical conductivity of the solution
- B) Lower the melting point of alumina
- C) Act as a reducing agent
- D) Remove impurities from the ore
Answer: B) Lower the melting point of alumina
Explanation: Cryolite is added to lower the melting point of alumina and increase the efficiency of the electrolytic extraction of aluminium.
75. The major impurity in iron extracted from the blast furnace is:
- A) Carbon
- B) Silica
- C) Sulphur
- D) Phosphorus
Answer: A) Carbon
Explanation: Pig iron, extracted from the blast furnace, contains a high percentage of carbon as the major impurity, making it brittle.
76. Which metal is obtained by the electrolysis of fused bauxite?
- A) Copper
- B) Aluminium
- C) Iron
- D) Zinc
Answer: B) Aluminium
Explanation: Aluminium is obtained by the electrolysis of fused alumina (extracted from bauxite) in the Hall-Héroult process.
77. Which of the following metals is refined by liquation?
- A) Zinc
- B) Lead
- C) Copper
- D) Aluminium
Answer: B) Lead
Explanation: Liquation is used for refining metals like lead and tin, where impurities have a higher melting point than the metal.
78. The ore haematite is an important source of:
- A) Aluminium
- B) Copper
- C) Iron
- D) Zinc
Answer: C) Iron
Explanation: Haematite (Fe2O3) is an important ore of iron, used as the primary source of iron in the blast furnace process.
79. Which of the following is not an ore of copper?
- A) Chalcopyrite
- B) Malachite
- C) Cuprite
- D) Siderite
Answer: D) Siderite
Explanation: Siderite (FeCO3) is an ore of iron, not copper. The other three are copper ores.
80. In the extraction of iron, the limestone added to the blast furnace:
- A) Acts as a flux
- B) Acts as a reducing agent
- C) Reduces the iron oxide to iron
- D) Produces carbon monoxide
Answer: A) Acts as a flux
Explanation: Limestone decomposes to form calcium oxide, which acts as a flux to remove silica impurities by forming slag.
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