The electrolysis of aqueous solutions
2 marks · HardDuring the electrolysis of concentrated sodium chloride solution, the volume of chlorine gas collected at the anode is often less than the volume expected. Explain two reasons for this observation.
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Also accept: Some chlorine dissolves in the solution; Some chlorine may react with water or impurities; Chlorine escapes before collection
Common mistakes: Only stating one reason; Saying chlorine is produced at the cathode
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Marking points
B1 · 1 mark · Mentions that chlorine gas is soluble in water and some of it dissolves rather than being collected.
B2 · 1 mark · Mentions that chlorine can react with the water or impurities, or can escape before being collected.
Worked solution
Chlorine gas is quite soluble in water, so some of it dissolves rather than being collected as gas. Also, some chlorine may react with water or impurities, or may escape before collection.