Molality calculations

Question

An aqueous solution was found to have an initial freezing point of -2.15C. what is the molality of the solution

Answer 1

This problem refers to colligative properties. You know the freezing point, you know the Kf constant for water(remember, it is an aqueous solution), 1.86 C·kg/mol, and you know the van't Hoff factor is 1.

 

ΔT_f = iK_fm

 

So -2.15 °C = (1)(1.86 C·kg/mol)m

 

And from there you can finish it off with a calculator.