Halogens 6.4 6.4 Silver Halides
KCl, KBr and KI (all aq) are all colourless, they can be identified by adding AgNO₃ which reacts to form a silver halide precipitate.
KCl_(aq) + AgNO_3(aq) → AgCl_(s) + KNO_3(aq)
Note that K⁺ and NO₃^- are spectator ions and so the ionic equation is:
Cl^-_(aq) + Ag⁺_(aq) → AgCl_(s) (spectators are ommitted in ionic equations)

Each of the silver halide precipiates has a slightly different colour (see right). This can be used to identify them. Ammonia solution can be used to more definately distinguish. AgCl dissolves in dilute, AgBr dissolves in concentrated (8M) and AgI doesn't dissolve. Or use light: AgCl → Purple, AgBr → Green, and AgI → No Change.

Colours of Silver Halides AgCl is White AgBr is Cream & AgI is Yellow