The newest 6 of 6 written questions. Open one to see it on the real paper.
The hydrogen gas is made by the electrolysis of water. During the electrolysis, hydrogen ions, H + , gain electrons. Hydrogen gas, H 2 , is made. Construct the ionic half-equation for this reaction. Use e – to represent an electron.
See it on the paper →Hydrogen gas, H 2 , is made at the negative electrode. Complete and balance the ionic half-equation for this reaction. –
See it on the paper →Aluminium is extracted from aluminium oxide by electrolysis. Aluminium ions, Al 3+ , make aluminium, Al. Construct the balanced ionic half-equation for the reaction.
See it on the paper →Copper atoms are formed from copper ions, Cu 2+ , at the cathode. Construct the balanced ionic half-equation for this reaction. Use the symbol e – for an electron.
See it on the paper →In the reaction between magnesium and zinc sulfate, magnesium ions, Mg 2+ , are formed from magnesium atoms. Construct the balanced ionic half-equation for this reaction. Use the symbol e – for an electron.
See it on the paper →What is the half-equation for the reaction at the cathode?
See it on the paper →The incorrect charge of 2+ was often seen on the hydrogen ion. Sometimes the hydrogen ion was not given a charge. Stronger candidates were able to complete the equation.
— Examiner report, February/March 2024, 0654/42 Q5(a)(iii) (Cambridge)
Many completely correct answers, only a relatively small number of candidates did not score on this question. An uncommon error, though one to be aware of, was to assign three negative charges to a single electron. A small number of candidates also included an ionic equation for the production of oxygen, impressive but did not receive any credit. Perhaps another case of read the question carefully...
— Examiner report, October/November 2023, 0654/43 Q8(c) (Cambridge)
Some candidates could construct the balanced half-equation for the discharge of copper ions.
— Examiner report, October/November 2022, 0654/41 Q11(c) (Cambridge)
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