The electrical conductivity of ionic substances
3 marks · EasyThe table shows three ionic compounds in different states:
| Compound | State |
|---|---|
| Sodium chloride | Solid |
| Magnesium bromide | Molten |
| Potassium nitrate | Aqueous |
Which compound(s) in the table will conduct electricity? State all correct answers.
State the condition required for any ionic compound to conduct electricity.
Give one example from the table where the ionic compound will not conduct electricity, and state why.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) Magnesium bromide (molten) and potassium nitrate (aqueous)
(b) The ions must be free to move (i.e. the substance is molten or dissolved in water).
(c) Sodium chloride (solid) will not conduct electricity because the ions are fixed in place.
Common mistakes: Listing solid instead of molten or aqueous for conduction.
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Marking points
B1 (a) · 1 mark · Correctly identifies both magnesium bromide (molten) and potassium nitrate (aqueous) as conducting.
B1 (b) · 1 mark · States correct general condition: ions must be free to move, so the substance is molten or in solution.
B1 (c) · 1 mark · States sodium chloride (solid) does not conduct and gives correct reason: ions are not free to move/fixed in place.
Worked solution
a. Magnesium bromide (molten) and potassium nitrate (aqueous) will conduct electricity. b. Any ionic compound will conduct electricity when its ions are free to move (molten or dissolved). c. Sodium chloride (solid) will not conduct electricity, because the ions are fixed in the lattice and cannot move.