This question is about the extraction and uses of sodium.
Sodium is extracted from molten sodium chloride NaCl\text{NaCl}NaCl by electrolysis. The positive electrode (anode) is made of graphite, and the negative electrode (cathode) is made of steel.
State why graphite is suitable for use as the positive electrode.
State why steel is suitable for use as the negative electrode.
Explain why the operating temperature would need to be very high (over 800∘C800^\circ\text{C}800∘C) if pure sodium chloride were used as the electrolyte.
Describe how the operating temperature of the electrolysis cell is kept lower.
The ionic half-equation for the reaction at the negative electrode is:
Na++e−→Na \text{Na}^+ + \text{e}^- \rightarrow \text{Na} Na++e−→NaWhat type of reaction is occurring at the negative electrode? Explain your answer.
Chlorine gas is produced at the positive electrode during this electrolysis. Describe how chlorine gas is formed from chloride ions.
Sodium is alloyed with potassium to make NaK, which is used as a heat-transfer coolant in specialized nuclear reactors.
State two properties of NaK that make it suitable for this use. You should not refer to cost in your answers.
21 exam-style questions on Edexcel IGCSE Chemistry Electrolysis. Each one has a worked solution and a mark scheme showing where the marks go.