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!
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.
Colligative properties are those that depend on the concentration of solute particles in a solution rather than the specific identity of the solute. The freezing point depression is one such colligative property.
The freezing point depression is the difference between the freezing point of a pure solvent (in this case, water) and the freezing point of a solution. It occurs because the presence of solute particles disrupts the formation of the crystal lattice structure in the solvent, making it more difficult for the solvent molecules to arrange themselves in an ordered manner necessary for freezing.
In this case, we are comparing two LiCl solutions with different concentrations: a 1.0m solution and a 0.10m solution. The concentration is expressed in moles of solute per liter of solution (mol/L) or molarity.
The freezing point depression is directly proportional to the molality (mol/kg) of the solute particles in the solution. Molality is the concentration of solute particles expressed in moles per kilogram of solvent.
To explain why the 1.0m solution of LiCl decreases the freezing point of water more than the 0.10m solution, we need to consider the number of solute particles that each solution contributes to the freezing point depression.
For a 1.0m solution, it means that there are 1.0 moles of LiCl solute particles present in 1.0 liter of solution. Since the solvent is water, which has a molar mass of approximately 18 g/mol, the mass of solvent (water) in the solution is approximately 1000 g.
Therefore, we can say that in the 1.0m solution, there are 1.0 moles of LiCl solute particles present in 1000 g (or 1 kg) of water.
For the 0.10m solution, it means that there are 0.10 moles of LiCl solute particles present in 1.0 liter of solution. Again, considering water as the solvent, the mass of solvent (water) in the solution is approximately 1000 g.
Therefore, in the 0.10m solution, there are 0.10 moles of LiCl solute particles present in 1000 g (or 1 kg) of water.
Comparing the number of solute particles between the two solutions, we can see that the 1.0m solution has a ten times higher concentration of LiCl solute particles compared to the 0.10m solution.
Considering that the freezing point depression is directly proportional to the molality of the solute particles, it means that the 1.0m solution will induce a greater decrease in the freezing point of water compared to the 0.10m solution. This is because there are more solute particles in the 1.0m solution to disrupt the formation of the crystal lattice in water and reduce its freezing point more significantly.