If the degree of dissociation of aqueous solution of weak monobasic...

$\mathop{HA}_{1 - \alpha} ⇋ \mathop{{H}^{+}}_{\alpha} + \mathop{{A}^{-}}_{\alpha}$

Van't Hoff factor, $i = 1 + \alpha\left(n - 1\right)$

$= 1 + 0 . 3\left(2 - 1\right)$

$= 1 + 0 . 3$

$= 1 . 3$

$∆ {T}_{f}$ without considering dissociation $= {k}_{f} \times$ molality

$∆ {T}_{f}$ without considering dissociation $= {ik}_{f} \times$ molality

$= {\Delta T}_{f}^{'}$

${\Delta T}_{f}^{'} - {\Delta T}_{f} = 0 . 3$ (${k}_{f} \times$ molality)

$\dfrac{{\Delta T}_{f}^{1} - {\Delta T}_{f}}{{\Delta T}_{f}} = \dfrac{0 . 3\left({k}_{f} \times molality\right)}{{k}_{f} \times molality} = 0 . 3$

$$ value $= 30$