Answer
$0.1\;g$.
Work Step by Step
The given values are
Base $B=20\;mL$.
Rate $R=(1:200)100=0.5$.
Let the pure silver nitrate is $P=x$.
The formula is
$\Rightarrow \frac{P}{B}=\frac{R}{100}$
Substitute all the values.
$\Rightarrow \frac{x}{20\;mL}=\frac{0.5}{100}$
Cross multiply.
$\Rightarrow 100x=10\;mL$
Divide both sides by $100$.
$\Rightarrow x=0.1\;mL$.
Convert $mL$ to $g$.
$\Rightarrow x=0.1\;mL\times \frac{1g}{1mL}$.
Simplify.
$\Rightarrow x=0.1\;g$.
