Which of the following aqueous solutions has the highest boiling point at 1.0 atm? Why?

Question

(A) 0.20 M CaCl₂

(B) 0.25 M Na₂SO₄

(C) 0.30 M NaCl

(D) 0.30 M KBr

(E) 0.40 M C₆H₁₂O₆

Answer 1

Raising the boiling point is a colligative property, and as such it depends on the concentration AND on the number of particles in solution. So, find the compound that produces the highest concentration with the most particles in solution, and that will be the answer.

(A) 0.20 M CaCl₂ => 3 particles x 0.2 M each = 0.6

(B) 0.25 M Na₂SO₄ => 3 particles x 0.25 M each = 0.75

(C) 0.30 M NaCl => 2 particles x 0.3 M each = 0.6

(D) 0.30 M KBr => 2 particles x 0.3 M each = 0.6

(E) 0.40 M C₆H₁₂O₆ => 1 particle x 0.4 M = 0.4

ANSWER = (B) will have the highest boiling point