Qualitative Analysis - Result Question 3
####3. In the following reaction sequence in aqueous solution, the species $X, Y$ and $Z$, respectively, are
(2016 Adv.)
$S _2 O _3^{2-} \xrightarrow{Ag^{+}} \underset{\text { (Clear solution) }}{X} \stackrel{Ag^{+}}{\longrightarrow} \underset{\text { (White ppt.) }}{Y} \xrightarrow{\text { With time }} \underset{\text { (Black ppt.) }}{Z}$
(a) $\left[Ag\left(S _2 O _3\right) _2\right]^{3-}, Ag _2 S _2 O _3, Ag _2 S$
(b) $\left[Ag\left(S _2 O _3\right) _3\right]^{5-}, Ag _2 SO _3, Ag _2 S$
(c) $\left[Ag\left(SO _3\right) _2\right]^{3-}, Ag _2 S _2 O _3, Ag$
(d) $\left[Ag\left(SO _3\right) _3\right]^{3-}, Ag _2 SO _4, Ag$
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Answer:
Correct Answer: 3. (a)
Solution:
- $2 S _2 O _3^{2-}+Ag^{+} \longrightarrow \underset{\text { (Clear solution) }}{\left.Ag\left(S _2 O _3\right) _2\right]^{3-}}$
$\left[Ag\left(S _2 O _3\right) _2\right]^{3-}+3 Ag^{+} \longrightarrow \underset{\text { (White ppt.) }}{2 Ag _2 S _2 O _3}$
$Ag _2 S _2 O _3+H _2 O \longrightarrow \underset{\text { (Black ppt.) }}{Ag _2 S+H _2 SO _4}$
