Iron and aluminium are two important metals extracted on a large scale.
In the extraction of iron, various raw materials and impurities are involved. Name the main chemical compound present in: (i) haematite (the principal ore of iron) (ii) the sedimentary rock added to the blast furnace to help remove acidic impurities
The following chemical equations represent reactions occurring in a blast furnace: A C(s)+O2(g)→CO2(g)\text{C(s)} + \text{O}_2\text{(g)} \rightarrow \text{CO}_2\text{(g)}C(s)+O2(g)→CO2(g) B CO2(g)+C(s)→2CO(g)\text{CO}_2\text{(g)} + \text{C(s)} \rightarrow 2\text{CO(g)}CO2(g)+C(s)→2CO(g) C 3Fe2O3(s)+CO(g)→2Fe3O4(s)+CO2(g)3\text{Fe}_2\text{O}_3\text{(s)} + \text{CO(g)} \rightarrow 2\text{Fe}_3\text{O}_4\text{(s)} + \text{CO}_2\text{(g)}3Fe2O3(s)+CO(g)→2Fe3O4(s)+CO2(g) D CaCO3(s)→CaO(s)+CO2(g)\text{CaCO}_3\text{(s)} \rightarrow \text{CaO(s)} + \text{CO}_2\text{(g)}CaCO3(s)→CaO(s)+CO2(g) E CaO(s)+SiO2(s)→CaSiO3(l)\text{CaO(s)} + \text{SiO}_2\text{(s)} \rightarrow \text{CaSiO}_3\text{(l)}CaO(s)+SiO2(s)→CaSiO3(l)
Choose from the letters A, B, C, D or E to answer the following. Each letter may be used once, more than once, or not at all. (i) An acid-base reaction that neutralizes the main acidic impurity (ii) A thermal decomposition reaction (iii) A highly exothermic combustion reaction that provides the main source of heat (iv) A redox reaction where carbon dioxide is reduced by carbon
Molten iron and a liquid byproduct called slag collect at the bottom of the blast furnace. State the chemical name and write the empirical formula of the main compound present in slag.
Aluminium is extracted from purified alumina (aluminium oxide) by electrolysis. (i) Explain, in terms of chemical reactivity, why carbon cannot be used to reduce aluminium oxide in a blast furnace. (ii) Explain the practical purpose of dissolving aluminium oxide in molten cryolite during the electrolysis process.
During the industrial extraction of aluminium by electrolysis, the carbon anodes have to be replaced periodically. Explain why this is necessary and support your answer with a balanced chemical equation.
The overall extraction of aluminium can be represented by the chemical equation:
2Al2O3→4Al+3O2 2\text{Al}_2\text{O}_3 \rightarrow 4\text{Al} + 3\text{O}_2 2Al2O3→4Al+3O2Write the two balanced ionic half-equations (including state symbols) representing the reactions occurring at the electrodes.
(i) Reduction half-equation at the cathode: (ii) Oxidation half-equation at the anode:
