2021 O Level Chem P1 Q6 — Ionic Compounds / Properties of Substances Solution

Answer: D. Silver chloride, AgCl, is an ionic compound, so it is a solid at room temperature with a high melting point. Ionic solids do not conduct electricity when solid (the ions are locked in the lattice) but do conduct when molten, because the ions are then free to move and carry charge.

Crucially, silver chloride is insoluble in water — all silver halides except silver fluoride are insoluble — so it cannot be dissolved to test conduction in solution.

Row D matches: solid at room temperature, does not conduct as a solid, conducts when molten, and is insoluble in water. A row that conducts as a solid would be a metal, and a row that dissolves would be a soluble ionic salt — neither is silver chloride.