\(\Delta T _{ b }= i \times K _{ b } \times m\)
The molality is equal to :
\(m=\frac{W_{ NaCl } \times 1000}{M_{ NaCl } \times W_{ H _{2} 0}( g )}\)
Therefore, the mass of \(NaCl\) can be calculated as :
\(1=2 \times 0.52 \times \frac{W_{ NaCl } \times 1000}{58.5 \times 500}\)
\(W_{ NaCl }=\frac{58.5 \times 500}{2 \times 0.52 \times 1000}\)
\(=28.125 \,g\)
(પાણી માટે $K_f =1.86\, K\, kg\,mol^{-1}$ છે )