Addition of a non-volatile solute to a pure solvent

ANS:D - both (b) and (c)

The correct answer is: both (b) and (c). When a non-volatile solute is added to a pure solvent:

1. Freezing Point: The presence of the solute disrupts the formation of the solvent's crystal lattice, so it takes a lower temperature to freeze the solution than it would to freeze the pure solvent. Hence, the freezing point decreases.
2. Boiling Point: The addition of a non-volatile solute elevates the boiling point of the solvent. This happens because the vapor pressure of the solution is lowered compared to that of the pure solvent, requiring a higher temperature for the solution to reach its boiling point.