11. Which of the following reactions occurs during the calcination process?
- A) 2ZnS+3O2→2ZnO+2SO2
- B) CaCO3→CaO+CO2
- C) 2FeS+3O2→2FeO+2SO2
- D) Cu2S+O2→Cu2O+SO2
Answer: B) CaCO3→CaO+CO2
Explanation: Calcination is the process of heating an ore in the absence or limited supply of air to remove volatile impurities. For example, in the calcination of limestone, calcium carbonate decomposes to form calcium oxide and carbon dioxide.
12. In the blast furnace, which zone is the hottest?
- A) Combustion zone
- B) Fusion zone
- C) Reduction zone
- D) Slag formation zone
Answer: A) Combustion zone
Explanation: The combustion zone, located at the bottom of the blast furnace, is the hottest part, where coke burns in the presence of oxygen to produce carbon dioxide and heat. This heat drives the other reactions occurring in the furnace.
13. Which of the following metals is extracted by using the electrolysis of its molten ore?
- A) Iron
- B) Copper
- C) Aluminium
- D) Zinc
Answer: C) Aluminium
Explanation: Aluminium is extracted by the electrolysis of molten alumina (Al2O3Al2O3) dissolved in molten cryolite. This method is used because aluminium is highly reactive, and it cannot be reduced by carbon like iron.
14. During the extraction of copper from copper matte, FeS is converted to FeO by:
- A) Roasting
- B) Smelting
- C) Calcination
- D) Electrolysis
Answer: A) Roasting
Explanation: Roasting involves heating copper matte in the presence of oxygen, during which iron sulphide (FeS) is oxidized to iron oxide (FeO) and sulphur dioxide gas is released.
15. Which of the following is removed as slag in the extraction of iron from its ore?
- A) Calcium silicate
- B) Iron silicate
- C) Ferric oxide
- D) Calcium oxide
Answer: A) Calcium silicate
Explanation: In the blast furnace, silica impurities in the ore react with lime (CaO) to form calcium silicate (CaSiO3), which is removed as slag.
16. The Ellingham diagram is used to predict the feasibility of:
- A) Roasting of ores
- B) Reduction of metal oxides
- C) Electrolysis of metals
- D) Leaching of ores
Answer: B) Reduction of metal oxides
Explanation: The Ellingham diagram is a graphical representation that helps predict the thermodynamic feasibility of the reduction of metal oxides by comparing the free energy changes of reactions at different temperatures.
17. In the extraction of copper by the electrorefining method, the impure copper is used as:
- A) Cathode
- B) Anode
- C) Electrolyte
- D) None of the above
Answer: B) Anode
Explanation: During electrorefining of copper, the impure copper is made the anode, and pure copper is deposited at the cathode. Impurities like silver and gold settle down as anode mud.
18. Which of the following is a primary source of iron in the blast furnace?
- A) Hematite
- B) Bauxite
- C) Calamine
- D) Malachite
Answer: A) Hematite
Explanation: Hematite (Fe2O3) is the primary ore of iron used in the blast furnace for extracting iron. It is reduced to iron by carbon monoxide in the furnace.
19. In the Bayer process, the major impurity present in bauxite is removed by:
- A) Heating with carbon
- B) Treating with sodium hydroxide
- C) Electrolysis
- D) Froth flotation
Answer: B) Treating with sodium hydroxide
Explanation: In the Bayer process, bauxite is treated with sodium hydroxide, which dissolves alumina, leaving behind impurities such as iron oxides and silica as insoluble residues.
20. Which of the following is used as a flux in the extraction of iron?
- A) Silica
- B) Limestone
- C) Alumina
- D) Sulphur dioxide
Answer: B) Limestone
Explanation: Limestone (calcium carbonate) is used as a flux in the extraction of iron. It decomposes to form calcium oxide, which then reacts with silica impurities to form slag.
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