Aqueous equations: charges, ions and redox evidence

Aqueous equations: charges, ions and redox evidence

Aqueous equations must conserve both atoms and charge. State symbols indicate whether a substance is solid, liquid, gas or aqueous, and they matter when deciding which ions are present. Strong soluble electrolytes are often written as ions in a complete ionic equation, while solids, liquids and weakly ionised substances remain together. Spectator ions appear unchanged on both sides and can be removed to show a net ionic equation. For redox evidence, compare oxidation numbers or explicitly show electron transfer; do not call a precipitation or dissolution reaction redox without that evidence.

Work it through

For AgNO₃(aq) + NaCl(aq) → AgCl(s) + NaNO₃(aq), the complete ionic view includes Ag⁺, NO₃⁻, Na⁺ and Cl⁻. Na⁺ and NO₃⁻ are spectators. The net ionic equation is Ag⁺(aq) + Cl⁻(aq) → AgCl(s). Atoms and total charge are balanced: +1 plus −1 gives zero on both sides.

Mastery target

Write or interpret a simple net ionic equation, identify spectator ions and check charge conservation before finalising an answer.