RP3: Aqueous Electrolysis with Inert Electrodes

In an electrolytic cell, an external supply drives a chemical change. The cathode is negative and the anode positive in this arrangement. Cations move toward the cathode and anions toward the anode, while electrons move through the external conducting circuit. Do not describe electrons as crossing the bulk solution in place of ions.

At the cathode, reduction involves gain of electrons. At the anode, oxidation involves loss of electrons. In aqueous solutions, water-derived species can also be involved, so the dissolved salt’s name alone does not identify every product. Use the stated electrolyte, concentration and electrode material.

Record bubbles, colour changes or deposits at identified electrodes. Where gases are collected or tested, use the centre’s approved small-scale method and the appropriate evidence: a hydrogen pop test, oxygen relighting a glowing splint, or chlorine bleaching damp indicator paper are distinct observations. Avoid treating bubbles alone as a unique gas identification.

With aqueous copper(II) sulfate and suitable inert electrodes, copper can deposit at the cathode while oxygen forms at the anode. The half-equation Cu²⁺ + 2e⁻ → Cu explains copper formation. For a different electrolyte or electrode, check the product rules and evidence again rather than copying the same labels.

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Copper electrodes in copper(II) sulfate provide a different anode process from inert graphite. Copper atoms can form copper ions at the anode while copper ions are reduced at the cathode. Compare the electrode masses using consistent washing and drying; retained solution can distort an apparent mass gain.

When comparing current, control the measurement interval, electrolyte and relevant geometry. Quantitative changes require actual initial and final masses, not a claim that blue colour alone measures deposited copper. In a suitable ideal model, charge is current × time, but interpret the measurements with electrode reactions and possible experimental losses.

Attempt these problems on paper before opening the worked reasoning. Explain your steps as well as giving a final answer.