1 . 2   mL of acetic acid is dissolved in water to make 2 . 0   L of solution. The depression in…

$\mathrm{M}=\mathrm{d}\times \mathrm{V}=1.02\times 1.2=1.224\mathrm{gm}$

Moles of acetic acid $=0.0204$ moles in $2 \mathrm{L}$

So molality $=0.0102 \mathrm{mol}/\mathrm{kg}$

Now ${\mathrm{\Delta T}}_{\mathrm{f}}=\mathrm{i}\times {\mathrm{K}}_{\mathrm{f}}\times \mathrm{m}$

$\mathrm{i}=1+\mathrm{\alpha }$ for acetic acid

$0.0198=\left(1+\mathrm{\alpha }\right)\times 1.85\times 0.0102$

$\mathrm{\alpha }=0.04928$

$\cong 5\%$