This question is about the extraction and uses of calcium.
Calcium is extracted from molten calcium chloride CaCl2\text{CaCl}_2CaCl2 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 770∘C770^\circ\text{C}770∘C) if pure calcium 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:
Ca2++2e−→Ca \text{Ca}^{2+} + 2\text{e}^- \rightarrow \text{Ca} Ca2++2e−→CaWhat 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.
Calcium is alloyed with other metals to make durable components such as maintenance-free lead-acid automotive batteries or structural components.
State two properties of calcium alloys that make them suitable for these uses. 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.