Question

A nonionizing solid dissolved in water change the freezing point to -2.79°C calculate its concentration.

Answer 1

Freezing point = 0 ºC – ΔT_f

$-2.79 = 0 - ΔT_f \\ ΔT_f = 2.79 \\ ΔT_f = K_f \times m \\ 2.79 = 1.86 \times m \\ m = \frac{2.79}{1.86} = 1.5 \;M$

Answer: 1.5 M