24.1.3—Calculate
- Syllabus
- 9701–2028–2029
- Objective
- 24.1.3
- Level
- A2
Use current and time to calculate electrolysis charge and product amount
Charge passed is Q = It, with current I in amperes and time t in seconds. Convert charge into moles of electrons using Q/F, then use the half-equation to find mass or gas volume.
The stoichiometric coefficient matters: depositing one mole of a 2+ metal needs two moles of electrons. Keep molar mass and gas-volume conditions separate from the electrochemical calculation.
A 2.00 A current for 965 s gives Q=1930 C and about 0.0200 mol e⁻. Cu²⁺ + 2e⁻ → Cu therefore deposits 0.0100 mol Cu.
Do not use minutes in Q=It or assume one electron per ion without reading the half-equation.
ConceptA-Level CAIE Chemistry A2