The flow diagram shows how aluminium is extracted in an industrial electrolysis cell.
Give the chemical name of purified ore P and of molten additive Q.
The chemical equations for several reactions occurring in the extraction and purification of aluminium are:
- A: Al3++3e−→Al\text{Al}^{3+} + 3\text{e}^- \rightarrow \text{Al}Al3++3e−→Al
- B: C+O2→CO2\text{C} + \text{O}_2 \rightarrow \text{CO}_2C+O2→CO2
- C: 2Al(OH)3→Al2O3+3H2O2\text{Al(OH)}_3 \rightarrow \text{Al}_2\text{O}_3 + 3\text{H}_2\text{O}2Al(OH)3→Al2O3+3H2O
- D: Al2O3+2NaOH+3H2O→2NaAl(OH)4\text{Al}_2\text{O}_3 + 2\text{NaOH} + 3\text{H}_2\text{O} \rightarrow 2\text{NaAl(OH)}_4Al2O3+2NaOH+3H2O→2NaAl(OH)4
- E: 2O2−→O2+4e−2\text{O}^{2-} \rightarrow \text{O}_2 + 4\text{e}^-2O2−→O2+4e−
Complete the table below by matching each type of reaction with the correct letter (A, B, C, D, or E). Each letter may be used once, more than once, or not at all.
| Type of reaction | Letter |
|---|---|
| one that is a thermal decomposition | |
| one where aluminium ions are reduced | |
| one that is a reaction of an amphoteric oxide with a base |
Aluminium is a highly reactive metal, yet it is highly resistant to corrosion in everyday environments. Name the compound that forms on its surface to provide this resistance, and the element in the air that reacts with aluminium to form it.
The order of reactivity of three metals is:
- Most reactive: zinc
- iron
- Least reactive: tin
Iron food cans and steel structural parts can be protected from rusting by coating them with a layer of zinc (galvanising) or tin. These protective coatings may become scratched during use.
Use the order of reactivity to suggest why coating iron with zinc continues to protect the iron even when scratched, whereas coating with tin can lead to rapid rusting of the iron once scratched.