The electrolysis of aqueous solutions
2 marks · EasyIn an experiment, 12 cm³ of hydrogen gas is collected at the cathode during the electrolysis of concentrated sodium chloride solution. The theoretical volume of chlorine expected at the anode is also 12 cm³, but only 7 cm³ is collected.
Calculate the difference between the expected and the actual volume of chlorine collected. Explain why there is this difference.
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5 cm³ less chlorine is collected than expected because chlorine is more soluble in water than hydrogen. cm³ (±0)
Also accept: chlorine dissolves in water; chlorine is soluble in water
Common mistakes: hydrogen dissolves instead of chlorine
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Marking points
M1 · 1 mark · Calculate the difference: 12 - 7 = 5 cm³.
M1 · 1 mark · State/explain: Chlorine is more soluble in water so not all is collected as a gas.
Worked solution
The difference is 12 cm³ - 7 cm³ = 5 cm³.
Less chlorine is collected than expected because chlorine is more soluble in water than hydrogen, so some chlorine dissolves and is not collected as a gas.