# Explain how the sign and magnitude of a standard cell potential (E°cell) can be used to predict whether a redox reaction is spontaneous under standard conditions.

> IB DP Chemistry Standard Level (2023 syllabus) — R3.2 Electron transfer reactions · Explain · 4 marks

> Standard electrode potentials are measured relative to the standard hydrogen electrode and used to determine the feasibility of redox reactions.

## Mark scheme (4 marks)

1. E°cell is calculated as E°(cathode/reduction) minus E°(anode/oxidation), or equivalently E°(more positive half-cell) minus E°(less positive half-cell).
2. A positive E°cell indicates the reaction is spontaneous (feasible) under standard conditions.
3. A negative E°cell indicates the reaction is non-spontaneous under standard conditions (the reverse reaction would be spontaneous).
4. The magnitude of E°cell indicates the relative driving force (tendency) of the reaction — a larger positive value corresponds to a greater tendency for the redox reaction to proceed spontaneously.

## Key terms

- [standard cell potential (E°cell)](https://www.gradenine.co.uk/glossary/standard-cell-potential-e-cell)

## Related

- [Revision notes for IB DP Chemistry Standard Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-sign-and-magnitude-81b8a2d6) · Published by Druglandscape Ltd.