Passing electricity through compounds: electrolysis
4 marks · NormalDescribe how you would set up an experiment to investigate the electrolysis of molten sodium chloride (). Include the apparatus you would use.
State one safety precaution that should be taken when carrying out this experiment.
What observation would show that electrolysis is taking place?
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.
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(a) Set up a crucible containing molten sodium chloride with two inert (carbon/platinum) electrodes inserted and connected to a power supply. · must show crucible or suitable container, molten sodium chloride, inert electrodes, power supply
(b) Wear heat-resistant gloves and eye protection, as molten is very hot. · must show safety precaution such as goggles, gloves, care with hot substances
(c) Bubbles of gas form at the electrodes or a change in the appearance of the electrodes. · must show visual evidence of gas or changes at electrodes
Common mistakes: Forgetting to mention molten compound or electrodes; omitting safety; vague observations.
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Marking points
M1 (a) · 1 mark · Correct mention of molten sodium chloride and use of an electrical circuit/electrodes.
M1 (a) · 1 mark · Names or describes appropriate apparatus, e.g. crucible, inert electrodes, power supply.
B1 (b) · 1 mark · States an appropriate safety precaution relevant to molten or electrical experiment.
B1 (c) · 1 mark · Describes an observation such as gas bubbles or a visible change at the electrodes.
Worked solution
a. Place molten sodium chloride in a heat-resistant crucible. Insert two inert carbon electrodes connected to a power supply so that they are dipped into the molten salt.
b. Wear heat-resistant gloves and eye protection because the crucible and contents are very hot.
c. Bubbles of gas are seen at the electrodes, or the surface of an electrode changes (e.g., metal deposits or charring).