Electrolysis

The anode product of molten lead(II) bromide is the element bromine, $\text{Br}_2$ — not "bromide" (that is the $\text{Br}^-$ ion in the starting compound), not "lead bromide" (the compound itself), and never hydrogen: there is no hydrogen anywhere in molten $\text{PbBr}_2$. Hydrogen only becomes a possible product once water is the solvent.

Electrolysing concentrated aqueous sodium chloride gives hydrogen at the cathode even though sodium ions are present in abundance. Sodium is the more reactive metal, so its ions stay in solution and the hydrogen ions supplied by the water are discharged instead. Sodium metal is obtained only from the molten, water-free compound.

Charge moves through the electrolyte by ions alone; electrons travel only through the wires and power supply of the external circuit. Writing that "electrons flow through the solution" confuses the two charge carriers. The electrolyte conducts precisely because its ions are free to move — which is also why a solid ionic compound will not conduct.

In copper purification (electrorefining) — copper electrodes in $\text{CuSO}_4$(aq) — the anode loses mass because copper atoms lose electrons and dissolve as $\text{Cu}^{2+}$ ions: $\text{Cu} \rightarrow \text{Cu}^{2+} + 2e^-$. Saying the anode "oxidises" in the everyday sense, or "loses oxygen", earns nothing. The pure copper cathode gains the mass the anode loses.

Oxidation = loss of electrons; reduction = gain of electrons. Candidates reverse this whenever they are asked which process happens at which electrode. At the cathode positive ions gain electrons, so that is reduction; at the anode particles lose electrons, so that is oxidation. OIL RIG is a memory aid, not the mark-scheme definition.

Candidates routinely reverse these, especially deep into a multi-part question. The anode is the positive electrode (joined to the positive terminal of the supply); the cathode is the negative one. Nothing about the product itself tells you the polarity, so state it explicitly every time rather than trusting a half-remembered mnemonic to hold up under pressure.

A full definition needs three linked ideas: the decomposition of an ionic compound, which must be molten or in aqueous solution, by the passage of an electric current. Dropping the molten/aqueous condition, or writing only "a compound breaks down", loses marks. Nor is the electrolyte "the electricity" or "the current" — it is the substance being decomposed.