Please answer the following questions thanks. why is molality, and not molarity, used to express concentration in the equations for freezing point

Please answer the following questions thanks.

1. why is molality, and not molarity, used to express concentration in the equations for freezing point depression and boiling point elevation?
2. assume that the solutes used in this experiment are soluble in both water and cyclohexane. why then was cyclohexane used as the solvent in this experiment?