Read Faraday's Laws Before Any Electrolysis Calculation
Electrolysis problems are Faraday's law problems — charge passed (I×t) converts to moles of electrons, which convert to moles of product via the half-reaction's own electron count.
Electrolysis & Conductance is the central idea in this question pattern. Identify the condition in the stem before applying the method below.
Charge to mass via Faraday's laws
Current × time gives total charge in coulombs; divide by Faraday's constant to get moles of electrons; divide by the half-reaction's electron count to get moles of the electrolysed species; multiply by its molar mass for the final mass — work through all four steps explicitly rather than jumping to a shortcut formula.
Electrode material changes the outcome, not just the mechanism
Electrolysing the same solution with active (reactive) electrodes versus inert electrodes can give different products entirely — an active electrode like Cu can dissolve at the anode instead of oxidising the solution's anion, changing whether pH shifts during electrolysis.
Molar conductivity from resistance and cell constant
chain these two relationships together to get from a measured resistance straight through to molar conductivity, keeping track of units at each step.
OlympIQ exam lens
- ✓Faraday's law chain: charge (I×t) → moles of electrons (÷F) → moles of product (÷electron count) → mass (×molar mass).
- ✓Active (reactive) electrodes can change what happens during electrolysis compared to inert electrodes — check which type is used.
- ✓Molar conductivity = (cell constant / resistance) / concentration — chain conductivity and concentration together carefully.
Don't assume inert electrodes when a question specifies a particular metal (like Cu) as the electrode — an active electrode can dissolve or plate out instead of driving the expected oxidation/reduction at that electrode.
Ready to try the pattern?
100% coverage across the 6 linked questions.
Practise 6 linked questions