The electrical conductivity of ionic substances
3 marks · EasyZinc chloride is an ionic compound.
Describe the movement of ions in solid zinc chloride.
Describe the movement of ions in molten zinc chloride.
Explain how movement of ions in the molten state affects electricity conduction.
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(a) Ions are held rigidly in place and cannot move.
(b) Ions are free to move in the liquid state.
(c) Moving ions can carry electrical charge, so the liquid conducts electricity.
Common mistakes: Mentioning electrons.
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Marking points
B1 (a) · 1 mark · Describes ions as fixed in solid zinc chloride.
B1 (b) · 1 mark · Describes ions as free to move in molten zinc chloride.
B1 (c) · 1 mark · Explains that moving ions carry charge so molten zinc chloride conducts electricity.
Worked solution
a. In solid zinc chloride, the ions are fixed in the lattice and cannot move. b. In molten zinc chloride, ions are free to move. c. Because ions can move in the liquid, they carry electrical charge and the molten substance conducts electricity.