5 g of fluoro acetic acid (molar mass =78 g mol^-1 ) is dissolved in 500 g of water at 298 K. The depression in the freezing point of water was 1^°…

$\displaystyle 5$ g of fluoro acetic acid (molar mass $\displaystyle =78 \mathrm{~g} \mathrm{~mol}^{-1}$ ) is dissolved in $\displaystyle 500$ g of water at $\displaystyle 298$ K . The depression in the freezing point of water was $\displaystyle 1^{\circ} \mathrm{C}$. What is $\displaystyle \mathrm{K}_{\mathrm{a}}$ of fluoro acetic acid ? (For water, $\displaystyle \mathrm{K}_{\mathrm{f}}=1.86 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}$ ). Assume molarity and molality to have same values.