The electrical conductivity of ionic substances
3 marks · NormalCopper(II) sulfate is an ionic compound. Predict and explain whether it will conduct electricity in each of these conditions: (a) as a solid (b) when dissolved in water. Give reasons for your answers.
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(a) Solid copper(II) sulfate does not conduct electricity because its ions are fixed in place and cannot move. (b) When dissolved in water, copper(II) sulfate conducts electricity because the ions are released and become free to move.
Must show: solid: does not conduct, ions fixed, aqueous: conducts, ions free
Also accept: Copper(II) sulfate only conducts electricity when aqueous because ions can move. In the solid, ions are held in place and cannot carry charge.
Common mistakes: Saying both conduct electricity; Confusing electrons and ions
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Marking points
B1 · 1 mark · States solid copper(II) sulfate does not conduct electricity.
B2 · 1 mark · Explains in solid, ions are fixed in place and cannot move.
B3 · 1 mark · Explains when dissolved in water, ions are free to move and so the substance conducts electricity.
Worked solution
(a) Solid copper(II) sulfate does not conduct because its ions are tightly held in the lattice and cannot move.
(b) In aqueous solution, the ions can move freely and carry electric current, so it conducts.