Question
An impure sample of silver $$\left( {1.5\,g} \right)$$ is heated with $$S$$ to form $$0.124\,g$$ of $$A{g_2}S.$$ What was the per cent yield of $$A{g_2}S?$$
A.
21.6 %
B.
7.2 %
C.
1.7 %
D.
24.8 %
Answer :
7.2 %
Solution :
\[\underset{\begin{smallmatrix}
2\times 108 \\
=216\,g
\end{smallmatrix}}{\mathop{2Ag}}\,+S\to \underset{248\,g}{\mathop{A{{g}_{2}}S}}\,\]
$$216{\text{ }}g{\text{ of }}Ag{\text{ forms }}248{\text{ }}g{\text{ of}}\,A{g_2}S$$
$$1.5\,g\,\,{\text{of}}\,\,Ag\,\,{\text{forms}}\,\,\frac{{248}}{{216}} \times 1.5$$ $$ = 1.722\,g\,\,{\text{of}}\,\,A{g_2}S$$
$$\% \,\,{\text{yield of}}\,\,A{g_2}S$$ $$ = \frac{{0.124}}{{1.722}} \times 100 = 7.2\% $$