Chemistry 5070 · O Level · Electrolysis

Electrolysis — practice question

The diagrams below show the structures of graphite and boron nitride.
(a)[2]

Just as graphite does, boron nitride feels slippery when touched. Explain, in terms of structure and bonding, why boron nitride feels slippery to the touch.

(b)[1]

An isotope of boron is shown by the symbol $^{11}_{5}\text{B}$. Deduce how many protons and neutrons are present in this isotope of boron.

(c)[2]

Explain why graphite has such a high melting point.

(d(i))[1]

Graphite is a good electrical conductor. Explain why graphite is able to conduct electricity.

(d(ii))[1]

Give one further property of graphite that makes it useful as an electrode in this electrolysis.

(e(i))[1]

In the electrolysis of dilute sulfuric acid, oxygen is produced at the anode (positive electrode) and hydrogen is produced at the cathode (negative electrode). Complete the equation for the reaction at the anode.\n\n$4\text{OH}^- \rightarrow \text{O}_2 + \ldots + \ldots$

(e(ii))[1]

Construct the equation for the cathode reaction.

(e(iii))[1]

Explain why the hydrogen volume produced is approximately twice the oxygen volume.

Worked solution & mark scheme

This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: weak van der Waals’ attractions between the layers

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