Question

A 1.0m solution of LiCl decreases the freezing point of water more than a .10 m solution of LiCl. Explain why based on colligative properties.

I know that the 1.0m solution would decrease it more, but cannot explain why. Any help is appreciated!

Answer 1

The solvent in a solution is what freezes. That happens when the forces of attraction between solvent molecules are great enough to overcome the kinetic energy of the molecules. When we add a solute to the solvent, the solvent molecules are farther apart and the temperature must be lowered more than normal because of the increased distance between solvent molecules. In a 1 m solution there are 10x more particles than in a 0.1m solution, the "field" is more crowded, and the temperature must be lowered more in order to offset the crowding brought about by the more concentrated solute.