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).
106 exam-style questions on Edexcel GCSE Chemistry 7.2 Group 7, covering 7.2.1 Physical properties of the halogens, 7.2.2 Reactions of the halogens, 7.2.3 Relative reactivity and displacement reactions of the halogens, and 7.2.4 Halogen displacement as a redox reaction. Each one has a worked solution and a mark scheme showing where the marks go.