Edexcel IGCSE Chemistry 1.58C electrolysis experiments

Practise electrolysis-experiment questions by choosing electrode products, explaining observations and justifying inert electrode materials.

Exam points

Predict electrode products from ions present in molten lead(II) bromide or aqueous salts.
Use reactivity to explain why hydrogen forms instead of sodium in sodium chloride solution.
Interpret observations such as bubbles, colour changes or deposits at each electrode.

[Maximum number: 3]

A scientist reacts lead(II) nitrate solution with sodium bromide solution.

This is the equation for the reaction.

\mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2}(\mathrm{aq})+2 \mathrm{NaBr}(\mathrm{aq}) \rightarrow \mathrm{PbBr}_{2}(\mathrm{~s})+2 \mathrm{NaNO}_{3}(\mathrm{aq})

(a)

The scientist electrolyses molten lead(II) bromide using this apparatus.

[ 2 ]

(i)

The electrolyte is at a temperature of $400^{\circ} \mathrm{C}$ .

Explain a suitable material for the electrodes.

[ 2 ]

(b)

Bromine forms at the positive electrode.

This is the half-equation for the reaction at the positive electrode.

2 \mathrm{Br}^{-} \rightarrow \mathrm{Br}_{2}+2 \mathrm{e}^{-}

[ 1 ]

(i)

State what is observed at the positive electrode.

[ 1 ]

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