Chemistry 9701 · AS & A Level · Group 17

Group 17 — practice question

Chlorine gas is produced by electrolysing brine in a diaphragm cell.
(a(i))

Give half-equations, including state symbols, for the reactions taking place at each electrode in a diaphragm cell. Anode and cathode.

(a(ii))[3]

In the diaphragm cell, the anode is made of titanium and the cathode is made of steel. Suggest why steel is unsuitable for use as the anode.

(b)[4]

Describe what you would see when chlorine is passed over separate heated samples of sodium and phosphorus. For each case, write an equation for the reaction.

(c)[4]

Chlorine reacts with aqueous sodium hydroxide in two different ways, depending on the conditions used. In each case, water, sodium chloride and one other chlorine-containing compound are made. For each condition below, give the formula of the other chlorine-containing compound and state the oxidation number of chlorine in it. cold dilute $\text{NaOH(aq)}$ hot concentrated $\text{NaOH(aq)}$

(d)[5]

Magnesium chloride, $\text{MgCl}_2$, and silicon tetrachloride, $\text{SiCl}_4$, each dissolve in or react with water. Suggest the approximate pH of the solution formed in each case. $\text{MgCl}_2$ $\text{SiCl}_4$ Explain, with the aid of an equation, why the two values differ.

Worked solution & mark scheme

This 16-mark question has a full step-by-step worked solution and mark scheme. One marking point: At the anode: $Cl^-(aq) \rightarrow \tfrac{1}{2}Cl_2(g) + e^-$

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