Question

A solution is made by dissolving 4.0 moles of sodium chloride (NaCl) in 2.05 kilograms of water. If the molal boiling point constant for water (Kb) is 0.51 °C/m, what would be the boiling point of this solution? Show all of the work needed to solve this problem.

Answer 1

Properties of a solution that depend only on the ratio of the number of particles of solute and solvent in the solution are known as colligative properties. For this problem, we use boiling point elevation concept.

ΔT(boiling point)  = (Kb)mi
ΔT(boiling point)  = (0.51 C-kg / mol )(4.0 mol / 2.05 kg ) (2)
ΔT(boiling point)  = 1.99 C

T(boiling point) = 101.99 C