Here below some basic MCQ’s about “Extraction of metals like Iron and Copper” with answer and explanation for exam practice. Let’s check one by one.
1. Which of the following is the most suitable reducing agent for the extraction of iron from its ore?
- A) Carbon monoxide
- B) Aluminium
- C) Hydrogen
- D) Sodium
Answer: A) Carbon monoxide
Explanation: In the blast furnace, iron is extracted from its ore, hematite (Fe2O3). Carbon monoxide acts as the reducing agent at high temperatures. It reduces iron ore to molten iron:
Fe2O3+3CO→2Fe+3CO2
2. In the extraction of copper from copper pyrites (CuFeS2CuFeS2), the role of silica is to:
- A) Act as a reducing agent
- B) Act as a flux to remove impurities
- C) Act as an oxidizing agent
- D) Reduce copper oxide to copper
Answer: B) Act as a flux to remove impurities
Explanation: In the extraction of copper, silica (SiO2SiO2) acts as a flux. It reacts with iron oxide (formed from iron impurities in copper pyrites) to form slag (iron silicate), which is removed from the furnace: FeO+SiO2→FeSiO3(slag)
3. Which process is used for the extraction of copper from low-grade ores?
- A) Froth flotation
- B) Leaching
- C) Smelting
- D) Roasting
Answer: B) Leaching
Explanation: For low-grade copper ores, the hydrometallurgical process of leaching is used. In this process, the ore is treated with acid or bacteria to dissolve the copper, which is later recovered by processes like solvent extraction or electro-winning.
4. The reaction in the blast furnace that produces slag during the extraction of iron involves:
- A) Carbon dioxide and lime
- B) Iron ore and limestone
- C) Calcium silicate and hematite
- D) Calcium oxide and silica
Answer: D) Calcium oxide and silica
Explanation: In the blast furnace, limestone (calcium carbonate) decomposes into calcium oxide (CaOCaO) and carbon dioxide. The calcium oxide reacts with silica (an impurity in iron ore) to form calcium silicate (slag), which is removed from the furnace: CaO+SiO2→CaSiO3(slag) (slag)
5. Which of the following is the main impurity present in the iron ore hematite?
- A) Silica
- B) Phosphorus
- C) Carbon
- D) Sulfur
Answer: A) Silica
Explanation: In the extraction of iron from hematite, the main impurity is silica (SiO2SiO2). This impurity is removed as slag by reacting with lime in the blast furnace.
6. Roasting of sulphide ores produces which of the following?
- A) Metal oxide
- B) Metal carbonate
- C) Metal sulphide
- D) Metal chloride
Answer: A) Metal oxide
Explanation: During roasting, sulphide ores are heated in the presence of oxygen, which converts the sulphide to oxide and releases sulfur dioxide gas: 2ZnS+3O2→2ZnO+2SO2
7. The froth flotation process is suitable for the concentration of which type of ores?
- A) Oxide ores
- B) Sulphide ores
- C) Carbonate ores
- D) Chloride ores
Answer: B) Sulphide ores
Explanation: Froth flotation is used to concentrate sulphide ores. In this process, the ore is mixed with water and a frothing agent, and air is blown through the mixture. The sulphide particles attach to the air bubbles and float to the surface, while the gangue sinks to the bottom.
8. Which of the following methods is used to extract iron from its ore?
- A) Electrolysis
- B) Reduction with carbon
- C) Leaching
- D) Magnetic separation
Answer: B) Reduction with carbon
Explanation: Iron is extracted from its ores (mainly hematite) by reduction with carbon in a blast furnace. The carbon reduces the iron oxide to molten iron, and carbon dioxide is produced as a byproduct.
9. What is the purpose of adding limestone in the extraction of iron in a blast furnace?
- A) To reduce iron ore to iron
- B) To remove impurities as slag
- C) To oxidize iron
- D) To produce carbon dioxide
Answer: B) To remove impurities as slag
Explanation: Limestone is added to the blast furnace to remove impurities. It decomposes to form calcium oxide, which then reacts with silica (the main impurity) to form slag.
10. The extraction of copper by the Bessemer process involves the oxidation of:
- A) Sulphur and iron impurities
- B) Carbon
- C) Silicon
- D) Calcium carbonate
Answer: A) Sulphur and iron impurities
Explanation: In the Bessemer process for copper extraction, air is blown through molten copper matte (a mixture of copper and iron sulphides). The air oxidizes the sulphur and iron impurities, which are then removed as slag or gas (as sulphur dioxide).
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