The electrolysis of aqueous solutions
4 marks · NormalA student electrolyses concentrated sodium chloride solution for several minutes and records the following results:
| Electrode | Gas | Volume collected (cm³) |
|---|---|---|
| Cathode | Hydrogen | 20 |
| Anode | Chlorine | 14 |
State the product collected at the cathode.
State the product collected at the anode.
Suggest a reason why less chlorine was collected than hydrogen.
Explain how the results could be used to confirm the identity of the hydrogen gas.
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.
Show answer
(a) Hydrogen
(b) Chlorine
(c) Chlorine dissolves in water
(d) Apply a lighted splint to collected gas; hydrogen 'pops' as it burns, confirming its identity
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Correctly states hydrogen at cathode
B2 (b) · 1 mark · Correctly states chlorine at anode
B3 (c) · 1 mark · Suggests that chlorine is more soluble, so less is collected
B4 (d) · 1 mark · Explains that hydrogen can be identified by the 'pop' sound with a lighted splint
Worked solution
a. Hydrogen is collected at the cathode.
b. Chlorine is collected at the anode.
c. Less chlorine is collected because it is soluble in water.
d. To confirm hydrogen, collect the gas and test it with a lighted splint. Hydrogen will 'pop' as it burns.