(a)(i) List two uses of aluminium and state how each use is related to the properties of the element.
(ii) State the reason why aluminium oxide is said to be amphoteric.
(b) Calcium is extracted by the electrolysis of fused calcium chloride containing about one-sixth of its mass of calcium fluoride.
(i) Sketch and label the cell used for the extraction.
(ii) Write equations for the reactions at the electrodes.
(iii) State the role of the calcium fluoride in the extraction.
(c) W, X, Y and Z represent four metals which have the following properties: W does not react with cold water but it liberates hydrogen from steam; X is one of the products formed when its trioxonitrate (V) decomposes on strong heating; Z forms the oxide when heated in air and it displaces W from an aqueous solutions of a salt of W; Y tarnishes rapidly exposure and reacts vigorously with cold water. Use the information provided to deduce the order of reactivity of the metals.
Explanation
(a)(i) Aluminium is usad for making cooking utensils because of its cheapness, low density, good appearance and good conductivity of heat and resistant to attack by cooking solutions. Aluminium is also used for making paint because of its shining nature.
(ii) Aluminium oxide is said to be amphoteric because it can exhibit both acidic and basic characters.
(b) The electrolysis of fused calcium chloride.
(ii) At cathode
Ca\(^{2+}\) + 2\(^-\) \(\to\) Ca (reduction)
At anode
2Cl\(^1\) \(\to\) Cl\(_2\) + 2e\(^-\) (an oxidation)
(iii) Calcium fluoride is an impurity in the electrolysis of the fused calcium chloride to the pure calcium.
(c) x, w, z, y
