We’re being asked to **identify which is true about the solutions regarding the colligative properties. **

Recall that the freezing point of a solution is *lower* than that of the pure solvent and the ** change in freezing point (ΔT_{f})** is given by:

$\overline{){{\mathbf{\Delta T}}}_{{\mathbf{f}}}{\mathbf{=}}{{\mathbf{T}}}_{\mathbf{f}\mathbf{,}\mathbf{}\mathbf{pure}\mathbf{}\mathbf{solvent}}{\mathbf{-}}{{\mathbf{T}}}_{\mathbf{f}\mathbf{,}\mathbf{}\mathbf{solution}}}$

The ** change in freezing point** is also related to the molality of the solution:

$\overline{){{\mathbf{\Delta T}}}_{{\mathbf{f}}}{\mathbf{=}}{{\mathbf{imK}}}_{{\mathbf{f}}}}$

where:

**i** = van’t Hoff factor

**m** = molality of the solution (in m or mol/kg)

**K _{f}** = freezing point depression constant (in ˚C/m) of the solvent

Recall that the boiling point of a solution is *higher* than that of the pure solvent and the ** change in boiling point (ΔT_{b})** is given by:

$\overline{){{\mathbf{\Delta T}}}_{{\mathbf{b}}}{\mathbf{=}}{{\mathbf{T}}}_{\mathbf{b}\mathbf{,}\mathbf{}\mathbf{solution}}{\mathbf{-}}{{\mathbf{T}}}_{\mathbf{b}\mathbf{,}\mathbf{}\mathbf{pure}\mathbf{}\mathbf{solvent}}}$

The ** change in boiling point** is also related to the molality of the solution:

$\overline{){{\mathbf{\Delta T}}}_{{\mathbf{b}}}{\mathbf{=}}{{\mathbf{imK}}}_{{\mathbf{b}}}}$

where:

**i** = van’t Hoff factor

**m** = molality of the solution (in m or mol/kg)

**K _{b}** = boiling point elevation constant (in ˚C/m) of the solvent

The problem states that we have aqueous solutions which means the solvent is water. This means the value of K_{f} is the same for all the given solutions.

Therefore, ΔT_{f} and ΔT_{b} will just depend on the osmolality of each solution, given by:

$\overline{){\mathbf{Osmolality}}{\mathbf{=}}{\mathbf{i}}{\mathbf{\times}}{\mathbf{m}}}$

A higher osmolality or concentration will result in a lower freezing point.

A higher osmolality or concentration will result in a higher boiling point.

If we have three different solutions, A, B, and C, each containing 100 g of water, plus respectively 6.84 g of sucrose (C _{12}H _{22}O _{11}), 0.72 g of ethanol, and 0.40 g of sodium hydroxide, which statement is true?

Frequently Asked Questions

What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the The Colligative Properties concept. You can view video lessons to learn The Colligative Properties. Or if you need more The Colligative Properties practice, you can also practice The Colligative Properties practice problems.