# How do you calculate the experimental molality of the methanol solution from the freezing point of the solution?

## $\Delta {T}_{f} = {K}_{f} m$

If you find ${K}_{f}$ and ${T}_{f}$ in a table for pure methanol, you can solve the equation for $m$ (molality of solution). Moreover, you can calculate the molar mass of an unknown solute to identify it in the lab.
For instance, if the freezing point of pure water is 0°C, but with the addition of salt it becomes -2.0°C, we can derive the molality of salt present.
Water K_f = (1.86°C)/m
2.0°C = (1.86°C)/m * m
$\therefore m \approx 1.1 m$