We’re being asked to determine the freezing point and boiling point of an aqueous Na₂SO₄ solution. Aqueous means that Na₂SO₄ was dissolved in water.

When calculating the freezing point of a solution, we’re going to use the Freezing Point Depression equation. On the other hand, when calculating for the boiling point of a solution we’re going to use the Boiling Point Elevation equation.

Freezing Point Depression:

∆T_f = change in freezing point = T_{f pure solvent} –T_{f solution}
K_f = freezing point depression constant
i = van' t Hoff factor of the solute = no. of ions
m = molality

Boiling Point Elevation: