Chemistry 5070 · O Level · Electrolysis

Electrolysis — practice question

(a)[2]

When concentrated aqueous magnesium iodide is electrolysed with graphite electrodes, what product is formed at each electrode?

(b)[2]

Using graphite electrodes, molten magnesium iodide is electrolysed. Write the ionic half-equation at each electrode for this electrolysis.

(c)[2]

Describe a test for iodide ions in aqueous solution. State what you would see if the test is positive.

(d(i))[1]

Explain, in terms of electron transfer, why iodide ions act as a reducing agent in this reaction: $2\text{I}^- + \text{MnO}_2 + 4\text{H}^+ \rightarrow \text{Mn}^{2+} + \text{I}_2 + 2\text{H}_2\text{O}$

(d(ii))[1]

State the name used for a reaction in which oxidation and reduction happen together.

(e)[2]

Finish Fig. 4.1 so that it shows the dot-and-cross diagram for a phosphorus(III) iodide molecule. Display only the outer-shell electrons.

Worked solution & mark scheme

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