Practise The process of electrolysis. 13 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
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What name is given to a liquid or solution that conducts electricity and is broken down by electrolysis?
electrolyte
A student electrolysed molten zinc chloride, ZnCl2, using inert electrodes. Give the name of the positive electrode.
anode
Name the electrode connected to the positive terminal of the power supply.
the anode
State which electrode, the cathode or the anode, is connected to the negative terminal of the power supply.
the cathode
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy4 marks
Electrolysis uses an electric current to break down ionic compounds.
(a) What name is given to a liquid or solution that conducts electricity and is broken down by electrolysis?[1]
(b) Solid sodium chloride does not conduct electricity. Molten sodium chloride does conduct electricity. Explain why.[2]
(c) Which electrode do positive ions move towards during electrolysis? Tick (✓) one box.[1]
the anode
the cathode
both electrodes
neither electrode
Show the answer and mark scheme
(a)Answer: electrolyte
electrolyte
(b)
in the solid the ions are held in fixed positions / cannot move
when molten the ions are free to move (and carry charge)
(c)Answer: the cathode
Question 2Medium5 marks
A student electrolysed molten zinc chloride, ZnCl2, using inert electrodes.
(a) Give the name of the positive electrode.[1]
(b) Which ions move towards the positive electrode? Explain why.[2]
(c) What is meant by an inert electrode?[1]
(d) Describe what happens to the ions when they reach the electrodes.[1]
Show the answer and mark scheme
(a)Answer: anode
anode
(b)
chloride ions / Cl−
they are negatively charged so are attracted to the positive electrode
(c)
an electrode that does not react (with the electrolyte or the products)
(d)
they are discharged: they gain or lose electrons to form atoms / molecules (elements)
Question 3Hard5 marks
A student placed a crystal of potassium manganate(VII) in the centre of a strip of filter paper soaked in sodium sulfate solution. Each end of the strip was connected to a d.c. power supply. After 20 minutes, a purple colour had spread from the crystal towards the positive electrode. Potassium manganate(VII) contains K+ ions and MnO4− ions.
(a) Which ion causes the purple colour? Explain your answer.[2]
(b) Suggest why the filter paper was soaked in sodium sulfate solution.[1]
(c) Potassium ions are colourless. Describe the movement of the potassium ions during the experiment.[1]
(d) Predict what would happen to the purple colour if the connections to the power supply were reversed.[1]
Show the answer and mark scheme
(a)
the manganate(VII) ion / MnO4−
it moved towards the positive electrode, so it must be negatively charged
(b)
so the paper contains ions that can move / so the paper conducts electricity (acts as an electrolyte)
(c)
they move towards the negative electrode / cathode
(d)
it would move in the opposite direction / back towards the new positive electrode