Arrange the following solutions in order of decreasing...

Arrange the following solutions in order of decreasing freezing point: $0.10 \mathrm{~m} \mathrm{Na}_{3} \mathrm{PO}_{4}, 0.35 \mathrm{~m} \mathrm{NaCl}$ $0.20 \mathrm{~m} \mathrm{MgCl}_{2}, 0.15 \mathrm{~m} \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}, 0.15 \mathrm{~m} \mathrm{CH}_{3} \mathrm{COOH}$

Key Concepts

Colligative Properties

Colligative properties are physical properties of solutions that depend only on the number of solute particles in the solvent, and not on the type of particles. Examples include freezing point depression, boiling point elevation, and osmotic pressure. The magnitude of these effects is influenced by the concentration of solute particles relative to the solvent.

Freezing Point Depression

Freezing point depression refers to the lowering of the freezing point of a solvent when a solute is dissolved in it. This effect is quantified by the formula ?Tf = i · Kf · m, where ?Tf is the change in freezing point, Kf is the cryoscopic constant of the solvent, m is the molality of the solution, and i is the van't Hoff factor.

Van't Hoff Factor

The van't Hoff factor (i) represents the number of particles into which a solute dissociates in solution. For ionic compounds that dissociate completely, i is equal to the total number of ions produced. This factor is crucial in calculating colligative properties because it determines the effective concentration of particles in the solution.

Molality

Molality is a concentration unit defined as the number of moles of solute per kilogram of solvent. It is particularly useful in colligative property calculations, such as freezing point depression, because it is not affected by changes in temperature unlike molarity.

Electrolyte and Non-Electrolyte Behavior

Electrolyte behavior refers to solutes that dissociate into ions in solution, thereby increasing the number of particles and significantly affecting colligative properties. Non-electrolytes do not dissociate in solution, so the number of particles remains the same as the number of dissolved molecules. Understanding the difference is essential when determining the overall effects on the freezing point.

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