How to find the percentage contribution of a compound via gravimetric analysis?
\begin{align}\ce{
3Ag + 4HNO3 &amp;-&gt; 3AgNO3 + NO + 2H2O\\
AgNO3 + KCl &amp;-&gt; AgCl + KNO3\\
}\end{align}
Moles of $\ce{AgCl} = 6.4/143.5 = 0.0446~\mathrm{mol}$

Mass of $\ce{Ag} = 0.0446 \cdot 108 = 4.816~\mathrm{g}$

Percentage of $\ce{Ag} = 4.816/5.2 \cdot 100=92.62\%$