Calculate $\Delta T_f$ of 0.15 m solution of nonvolatile solute $\left[\mathrm{K}_{\mathrm{f}}=1 \cdot 5 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}\right]$

The depression in freezing point $\Delta T_f$ is determined using the colligative property formula $\Delta T_f = i \cdot K_f \cdot m$, where $i$ is the van't Hoff factor, $K_f = 1.5 \text{ K kg mol}^{-1}$ is the cryoscopic constant, and $m = 0.15 \text{ m}$ is the molality.

For a nonvolatile, non-electrolyte solute, $i = 1$.

Substituting the values:

$\Delta T_f = 1 \cdot 1.5 \cdot 0.15 = 0.225 \text{ K}$

The result corresponds to option C.