Extraction of Metals Quiz

1. Which statement correctly explains why metals low in the reactivity series are easier to extract from their ores?

• A. They require less energy because they form weaker bonds with oxygen
• B. They are found in larger quantities in the Earth's crust
• C. They do not need to be reduced from their oxides
• D. They can be extracted using carbon alone without any heating

2. In the blast furnace extraction of iron, what is the primary role of carbon monoxide?

• A. To provide heat for the furnace reactions
• B. To reduce iron(III) oxide to iron metal
• C. To form slag with impurities
• D. To decompose calcium carbonate

3. Why is cryolite used during the electrolytic extraction of aluminium from purified bauxite?

• A. It acts as an oxidising agent to remove impurities
• B. It lowers the melting point of aluminium oxide, making the process more economical
• C. It prevents the formation of oxygen gas at the cathode
• D. It increases the conductivity of pure aluminium oxide, which is a poor conductor

4. In the blast furnace, calcium carbonate undergoes thermal decomposition. What is the purpose of the calcium oxide product?

• A. It reduces iron(III) oxide to produce iron
• B. It removes silica impurities by forming slag
• C. It provides additional heat for the reduction reactions
• D. It oxidises carbon to carbon dioxide

5. At the anode during aluminium electrolysis, carbon is oxidised and regularly needs replacing. Which half-equation represents this oxidation process, and why must the anode be replaced?

• A. C + 4e⁻ → C⁴⁻; because carbon is reduced to carbide
• B. C + 2O²⁻ → CO₂ + 4e⁻; because carbon reacts with oxygen ions produced at the anode and is gradually consumed
• C. O₂ + 4e⁻ → 2O²⁻; because oxygen is consumed in the reaction
• D. 2O²⁻ → O₂ + 4e⁻; because the anode produces oxygen that escapes as gas