Gold and iron extraction are important mining processes in South Africa. Refining takes
place according to the following reactions:
Gold is dissolved using cyanide ions (CN–) to extract it from the ore:
4Au(s) + 8NaCN(aq) + 2H2O(ℓ) + O2(g) → 4NaAu(CN)2(aq) + 4NaOH(aq)
Iron(lll)oxide is burned in a furnace in the presence of CO:
Fe2O3(s) + 3CO(s) → 2Fe(ℓ) + 3CO2(g)
10.1 Name TWO disadvantages of deep-shaft mining in comparison with open-cast mining. (2)
10.2 Write down the FORMULA of the substance that is reduced in the reaction
used to extract gold. (1)
10.3 Use oxidation numbers to explain how you arrived at the answer to
QUESTION 10.2. (1)
10.4 Write the reduction half-reaction for the iron extraction reaction. (2)
10.5 Calculate the percentage of iron present in Fe2O3. (2)
10.6 Only 65% of the ore contains iron. If 2 500 kg of ore is used, calculate the
mass of iron that can be extracted from the ore. (2)
[10]
TOTAL: 150