VCE · Topic explainer

How do you use the electrochemical series?

The electrochemical series orders half-reactions by standard reduction potential. For two suitable half-cells under standard conditions, the higher potential is the reduction at the cathode. Reverse the lower-potential half-reaction for oxidation at the anode. Subtract the anode’s listed reduction potential from the cathode’s to predict the standard cell voltage.

Worked example

The VCAA data book lists Ag⁺/Ag at +0.80 V and Cu²⁺/Cu at +0.34 V. For a silver–copper cell, silver ions are reduced and copper metal is oxidised. The standard voltage is 0.80 − 0.34 = 0.46 V.

Balance electrons by doubling the silver half-equation. Electrode potential is a voltage, so keep +0.80 V unchanged when you double the equation. The overall reaction is Cu(s) + 2Ag⁺(aq) → Cu²⁺(aq) + 2Ag(s).

Ag⁺/Ag: +0.80 V, reduction. Cu²⁺/Cu: +0.34 V, reverse to oxidise. Standard voltage: +0.46 V.

Official exam practice

2023 VCE Chemistry, Section A, Question 28, previous study design

Find other years and marking guidance in the Chemistry official exam archive.

Further reading. VCAA 2025 Chemistry examination and data book, electrochemical series