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Q. One given of a monobasic acid dissolved in $200 \,g$ of water lowers the freezing point by $0.186^{\circ} C$. On the other hand, when $1 \,g$ of the same acid is dissolved in water so as to make the solution $200\, mL$, this solution requires $125 \,mL$ of $0.1 \,N\, NaOH$ for complete neutralization. Calculate $\alpha$ for the acid in percent. $\left( K _{ f }=1.86 \,K \,kg\, mol ^{-1}\right)$

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Solution:

$\frac{1}{M_{\text {acid }}}=\frac{125}{1000} \times 0.1$
$\Rightarrow M _{\text {acid }}=80\, g\, mol ^{-1}$
$0.186=(1+\alpha) \times 1.86 \times\left[\frac{\frac{1}{80}}{0.2}\right]$
$\Rightarrow \alpha=0.6 \Rightarrow 60 \%$