$d$દ્રાવણ $=1.25 \mathrm{~g} / \mathrm{mL}]$
\(=500 \times 1.25=625 \mathrm{~g}\)
\(\text { Mass of solute }(x)=0.2 \times 0.5 \times 159.5\)
\(=15.95\)
\(\mathrm{n}_{\text {solute }}=0.1 \text {, }\)
\(\text { Mass of solvent }=\text { Mass of solution }- \text { Mass of solute }\)
\(=625-15.95\)
\(=609.05\)
\(\mathrm{~m}=\frac{0.1}{\frac{609.05}{1000}}\)
\(\mathrm{~m}=0.164=164 \times 10^{-3}\)