Spectator ion

[phiryn]

How do we know when to ignore the anion or the cation during pH calculations of salts? I know Dr. Lavelle mentioned about a certain molecule picking up the H, but what are the rules or specifics of knowing?

[Chloe Alias 1D]

Ignore the ion that comes from a strong acid or base, and consider the ion that comes from a weak acid or base. If both ions come from weak acids/bases, consider both and assess their relative strength.