The electrolysis of aqueous solutions
3 marks · NormalExplain why it is important not to completely cover the electrodes with the test tubes when setting up the apparatus to investigate the electrolysis of aqueous sodium chloride solution.
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Also accept: Complete covering stops current flow; Ions can't move
Common mistakes: Thinking it only prevents gas collection
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Marking points
M1 · 1 mark · States that complete covering blocks ion flow
A1 · 1 mark · Explains that current will not flow if ions cannot move
A2 · 1 mark · Relates to why this is important for electrolysis to occur (no reaction if no current)
Worked solution
If the test tubes completely cover the electrodes, ions in the solution cannot move to the electrodes. This stops the flow of electrical current. Without current, electrolysis does not occur, so no products will form at the electrodes.