1 . 2mL of acetic acid is dissolved in water to make 2 . 0L of...

$M = d \times V = 1 . 02 \times 1 . 2 = 1 . 224gm$

Moles of acetic acid $= 0 . 0204$ moles in $2L$

So molality $= 0 . 0102mol / kg$

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

$i = 1 + \alpha$ for acetic acid

$0 . 0198 = \left(1 + \alpha\right) \times 1 . 85 \times 0 . 0102$

$\alpha = 0 . 04928$

$≅ 5$