c
\(\frac{{{p^0} - p}}{{{p^0}}} = \frac{{W \times {M_0}}}{{M \times {W_0}}}\)

\(\therefore \,\,\,\,\frac{{25 - 24.5}}{{25}} = \frac{{W \times 1000 \times {M_0}}}{{M \times {W_0} \times 1000}}\) (\(1000\) વડે  ગુણીને ભાગતાં)

\(\therefore \frac{{0.5}}{{25}} = \) (મોલાલિટી) / \(1000\)  \( \times {M_0}\)

મોલાલિટી \( = \frac{{500}}{{25 \times 18}} = \frac{{20}}{{18}} = 1.11\)