An aqueous solution of potassium sulfate (K2SO4) has a freezing point of -2.24C. What is its molality? (Kf=1.86C m-1)
To find the molality of the solution, we need to calculate the change in freezing point.
Change in freezing point = freezing point of the solvent - freezing point of the solution
= 0°C - (-2.24°C) = 2.24°C
The molality (m) of a solution is defined as the moles of solute per kilogram of solvent.
We know that the freezing point depression (ΔTf) is related to the molality by the formula:
ΔTf = Kf * m
Rearranging the formula, we can solve for the molality:
m = ΔTf / Kf
= 2.24°C / 1.86°C m^-1
≈ 1.20 mol/kg
Therefore, the molality of the potassium sulfate solution is approximately 1.20 mol/kg.