Practical: Investigating the Electrolysis of Aqueous Solutions — Electrolysis | IGCSE Chemistry | Examo

Practical: Investigating the Electrolysis of Aqueous Solutions — Electrolysis | IGCSE Chemistry | Examo

Exam Frequency Analysis

Past paper frequency (2018 to 2024)

This topic accounts for approximately 7% of your exam marks.

stable

Low

Stable7%

Electrode products, half-equations and OILRIG tested in most series.

Goal of the practical

Pass a current through aqueous NaCl, dilute H₂SO₄ and CuSO₄, then collect and test whatever is released at the cathode and the anode for each electrolyte

Apparatus and method

A beaker containing the solution to be electrolysed
Two inert graphite electrodes dipping into the liquid, connected to a low-voltage d.c. power supply
Two small test tubes are filled with the same solution and inverted over the electrodes so that any gas produced collects inside them
Switch on the supply, allow electrolysis to proceed until enough gas (or solid) has formed, then switch off and test the products

Identifying the products

A gas that gives a pop with a lighted splint is hydrogen
A gas that relights a glowing splint is oxygen
A gas that bleaches damp blue litmus paper is chlorine
A solid coating that builds up on the cathode is the metal — its colour is a clue to its identity (pink-brown for copper)

Results

Electrolyte	At the cathode	At the anode
Sodium chloride	Colourless gas, pops with a lighted splint (hydrogen)	Pale yellow-green gas, bleaches damp blue litmus (chlorine)
Dilute sulfuric acid	Colourless gas, pops with a lighted splint (hydrogen)	Colourless gas, relights a glowing splint (oxygen)
Copper(II) sulfate	Pink-brown solid builds up on the electrode (copper)	Colourless gas, relights a glowing splint (oxygen)