If 1 mole of each of the solutes listed below is dissolved in 1 L of water, which solute will have the greatest effect on the vapor pressure of its respective solution?

Question

Which is the correct answer?

A) C6H12O6

B) CaSO4

C) KBr

D) MgCl2

Answer 1

When concentration and all else are the same, the vapor pressure will depend on the NUMBER of particles.

A) C₆H₁₂O₆ (glucose) produces 1 particle

B) CaSO₄ produces 2 particles; Ca²⁺ and SO₄^2-

C) KBr produces 2 particles; K⁺ and Br^-

D) MgCl₂ produces 3 particles: Mg²⁺ and 2Cl^-

Thus D (MgCl₂) will have the greatest effect on vapor pressure.