The electrolysis of other molten substances
2 marks · EasyBalance the following ionic half-equation for the electrolysis of molten calcium chloride so that both atoms and charges balance:
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Ca^{2+} + 2e^- \to Ca
Also accept: Include state symbols if given
Common mistakes: Using 1 electron only
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Marking points
M1 · 1 mark · Identifies that the number of electrons must balance the charge on Ca^{2+}.
A1 · 1 mark · Correctly writes balanced half-equation: Ca^{2+} + 2e^- \to Ca.
Worked solution
The Ca^{2+} ion has a 2+ charge, so 2 electrons are needed to balance the charge.