Chemistry 5070 · O Level · Electrolysis

Electrolysis — practice question

(a)[2]

A concentrated aqueous solution of calcium bromide is electrolysed with graphite electrodes. Predict the substance formed at each electrode.

(b)[2]

Graphite electrodes are used to electrolyse molten calcium bromide. Construct the ionic half-equation for the change at each electrode when molten calcium bromide is electrolysed.

(c)[2]

Describe a test for aqueous bromide ions. Include what is seen if the result is positive.

(d(i))[1]

Explain, in terms of electron transfer, how calcium acts as a reducing agent in the equation $\text{Ca} + \text{Zn}^{2+} \rightarrow \text{Zn} + \text{Ca}^{2+}$.

(d(ii))[1]

State the oxidation number for the $\text{Zn}^{2+}$ ion.

(e)[2]

Sulfur dibromide is formed when sulfur reacts with bromine. Complete Fig. 4.1 to show the dot-and-cross diagram for a molecule of sulfur dibromide. Show only the outer shell electrons.

Worked solution & mark scheme

This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: anode product: bromine

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