Chemistry 0620 · IGCSE · Electrolysis

Electrolysis — practice question

At room temperature, potassium reacts with bromine to produce potassium bromide.
(a)[3]

Construct a chemical equation for this reaction, making sure to show state symbols.

(b(i))[2]

What does the term ionic lattice mean?

(b(ii))[2]

Explain why potassium bromide does not conduct electricity in the solid state but does conduct electricity when molten.

(c(i))[2]

What is the meaning of the term electrolyte?

(c(ii))[4]

Describe the electrolysis of concentrated aqueous potassium bromide. Include: an ionic half-equation for the reaction at the cathode, the name of the product at the anode, and the name of the potassium compound that is formed.

(c(iii))[1]

When molten potassium bromide is electrolysed, the cathode product is different. Name the substance formed at the cathode during electrolysis of molten potassium bromide.

(d(i))[2]

Write a chemical equation to represent this reaction.

(d(ii))[2]

Draw a dot-and-cross diagram to show how electrons are arranged in a molecule of iodine monochloride. Show only the outer-shell electrons.

(e)[3]

Using attractive forces, explain why these melting points are so different.

(f(i))[1]

Write an ionic half-equation to show what happens to the chlorine molecules, $\text{Cl}_2$, in this reaction.

(f(ii))[1]

Explain why the bromide ions, $\text{Br}^-$, behave as reducing agents in this reaction.

Worked solution & mark scheme

This 23-mark question has a full step-by-step worked solution and mark scheme. One marking point: The balanced equation is $\text{2K(s)} + \text{Br}_2\text{(l)} \rightarrow \text{2KBr(s)}$.

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