E(Cu2+/Cu) = +0.34 V and E(Zn2+/Zn) = -0.76 V. Calculate the standard EMF and state the spontaneous reaction direction.
[3 marks]
Total for this question: 3
All calculations
Cell EMF from electrode potentials
Electrode potentials
AQA 7405
ORIGINAL
Ecell = E(reduction at positive electrode) - E(reduction at negative electrode)
Keep both values as reduction potentials: more positive minus more negative.
Board and spec code confirmed against AQA 7405 · registry checked 2026-07-11How this checking works
Work it, then mark it
Do each calculation on paper first, then reveal the mark scheme and tick the marks you actually earned — the same way you should mark past papers.
Q1
Do the calculation on paper first — then mark it.
Where the marks get lost
- Adding a negative potential without brackets.
- Reversing a half-equation and also changing the tabulated E value's sign.
Exam tip: Tabulated values stay as reduction potentials; subtract the less positive value from the more positive value.
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