Question
In the following reaction sequence in aqueous solution, the species $$X,Y\,{\text{and}}\,Z,$$ respectively, are
\[{{S}_{2}}O_{3}^{2-}\xrightarrow{A{{g}^{+}}}\underset{\begin{smallmatrix}
\text{clear} \\
\text{solution}
\end{smallmatrix}}{\mathop{X}}\,\xrightarrow{A{{g}^{+}}}\underset{\begin{smallmatrix}
\text{white} \\
\text{precipitate }
\end{smallmatrix}}{\mathop{Y}}\,\] \[\xrightarrow{\text{with time }}\underset{\text{black precipitate }}{\mathop{Z}}\,\]
A.
$${\left[ {Ag{{\left( {{S_2}{O_3}} \right)}_2}} \right]^{3 - }},A{g_2}{S_2}{O_3},A{g_2}S$$
B.
$${\left[ {Ag{{\left( {{S_2}{O_3}} \right)}_3}} \right]^{5 - }},A{g_2}S{O_3},A{g_2}S$$
C.
$${\left[ {Ag{{\left( {S{O_3}} \right)}_2}} \right]^{3 - }},A{g_2}{S_2}{O_3},Ag$$
D.
$${\left[ {Ag{{\left( {S{O_3}} \right)}_3}} \right]^{3 - }},A{g_2}S{O_4},Ag$$
Answer :
$${\left[ {Ag{{\left( {{S_2}{O_3}} \right)}_2}} \right]^{3 - }},A{g_2}{S_2}{O_3},A{g_2}S$$
Solution :
\[{{S}_{2}}O_{3}^{2-}\xrightarrow{A{{g}^{+}}}\underset{\begin{smallmatrix}
\left( X \right) \\
\text{clear solution }
\end{smallmatrix}}{\mathop{{{\left[ Ag{{\left( {{S}_{2}}{{O}_{3}} \right)}_{2}} \right]}^{3-}}}}\,\] \[\xrightarrow{A{{g}^{+}}}\underset{\begin{smallmatrix}
\left( Y \right) \\
\text{white precipitate }
\end{smallmatrix}}{\mathop{A{{g}_{2}}{{S}_{2}}{{O}_{3}}\downarrow }}\,\xrightarrow{\text{on standing }}\underset{\begin{smallmatrix}
\left( Z \right) \\
\text{black precipitate }
\end{smallmatrix}}{\mathop{A{{g}_{2}}S\downarrow }}\,\]
So, $$X,Y\,{\text{and}}\,Z\,{\text{are}}$$ $${\left[ {Ag{{\left( {{S_2}{O_3}} \right)}_2}} \right]^{3 - }},A{g_2}{S_2}{O_3}\,{\text{and}}\,A{g_2}S$$ respectively.