An analytical chemist is identifying an unknown halide ion, X−\text{X}^-X−, in an industrial wastewater sample. The chemist adds acidified silver nitrate solution, AgNO3(aq)\text{AgNO}_3(\text{aq})AgNO3(aq), to the sample, yielding a cream precipitate. They then perform solubility tests on this precipitate using aqueous ammonia, NH3(aq)\text{NH}_3(\text{aq})NH3(aq).
Which option correctly describes the identity of the precipitate and its subsequent behavior and reaction with ammonia?
The precipitate is AgBr(s)\text{AgBr}(\text{s})AgBr(s). It is insoluble in dilute NH3(aq)\text{NH}_3(\text{aq})NH3(aq) but dissolves in concentrated NH3(aq)\text{NH}_3(\text{aq})NH3(aq) to form the complex ion [Ag(NH3)2]+(aq)[\text{Ag}(\text{NH}_3)_2]^+(\text{aq})[Ag(NH3)2]+(aq).
The precipitate is AgI(s)\text{AgI}(\text{s})AgI(s). It is insoluble in dilute NH3(aq)\text{NH}_3(\text{aq})NH3(aq) but dissolves in concentrated NH3(aq)\text{NH}_3(\text{aq})NH3(aq) to form the complex ion [Ag(NH3)2]+(aq)[\text{Ag}(\text{NH}_3)_2]^+(\text{aq})[Ag(NH3)2]+(aq).
The precipitate is AgBr(s)\text{AgBr}(\text{s})AgBr(s). It is soluble in dilute NH3(aq)\text{NH}_3(\text{aq})NH3(aq) to form the complex ion [Ag(NH3)2]+(aq)[\text{Ag}(\text{NH}_3)_2]^+(\text{aq})[Ag(NH3)2]+(aq).
The precipitate is AgBr(s)\text{AgBr}(\text{s})AgBr(s). It is insoluble in dilute NH3(aq)\text{NH}_3(\text{aq})NH3(aq) but dissolves in concentrated NH3(aq)\text{NH}_3(\text{aq})NH3(aq) to form the complex ion [Ag(NH3)4]+(aq)[\text{Ag}(\text{NH}_3)_4]^+(\text{aq})[Ag(NH3)4]+(aq).
Practise Edexcel GCSE Chemistry Group 7 with exam-style questions for Foundation and Higher tier. 87 questions, matched to the Edexcel GCSE Chemistry (1CH0) specification and written in Paper 1 and Paper 2 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.