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In the given reaction sequence occurring in an aqueous medium, identify the species X, Y, and Z in the following steps: S2O3²− reacts with Ag+ to form X (a clear solution), which further reacts with Ag+ to produce Y (a white precipitate). Over time, Y transforms into Z (a black precipitate).

1. [As(S2O3)2]3−, Ag2S2O3, Ag2S
2. [Ag(S2O3)3]5−, Ag2S2O3, Ag2S
3. [Ag(SO3)2]3−, Ag2S2O3, Ag
4. [Ag(SO3)3]3−, Ag2SO4, Ag

Correct answer: [As(S2O3)2]3−, Ag2S2O3, Ag2S

Solution

S₂O₃²⁻ reacts with Ag⁺ to form a soluble complex [Ag(S₂O₃)₂]³⁻ (X). Further reaction with Ag⁺ produces Ag₂S₂O₃ (Y), which is a white precipitate. Over time, Y decomposes to form Ag₂S (Z), a black precipitate.

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