CH-1724

Half-equations

Chemistry · Secondary 4 · Medium · Half-equations

A student electrolyses aqueous copper(II) sulfate using inert graphite electrodes. Which half‑equation correctly represents the reaction at the cathode?

$Cu^{2+}(aq) + 2e^- \rightarrow Cu(s)$
$Cu(s) \rightarrow Cu^{2+}(aq) + 2e^-$
$2H_2O(l) \rightarrow O_2(g) + 4H^+(aq) + 4e^-$
$SO_4^{2-}(aq) + 2e^- \rightarrow SO_3^{2-}(aq) + O^{2-}(aq)$

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