Testing for chlorides (Cl^-), bromides (Br^-) and iodides (I^-)
2 marks · NormalState the names and colours of the precipitates formed when silver nitrate is added to (a) a solution containing bromide ions and (b) a solution containing iodide ions, after acidification with nitric acid.
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Must show: 'silver bromide, cream' for bromide ions, 'silver iodide, yellow' for iodide ions
Also accept: Name then colour, or colour then name; allow correct formulae (AgBr, AgI) as alternatives
Common mistakes: Swapping colours (e.g. saying yellow for bromide, cream for iodide); Giving 'silver nitrate' as the precipitate
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Marking points
B1 · 1 mark · Names and colour for bromide: silver bromide, cream (allow AgBr, cream)
B1 · 1 mark · Names and colour for iodide: silver iodide, yellow (allow AgI, yellow)
Worked solution
(a) Bromide ions: silver bromide, cream precipitate (or AgBr, cream).
(b) Iodide ions: silver iodide, yellow precipitate (or AgI, yellow).