MU #1 The addition of a nonvolatile solute to a solvent causes the boiling point of the solvent to increase and the freezing point of the solvent to decrease. 

Example

For every mole of particles added to1 kg of pure water the freezing point decreases by 1.86^oC and the boiling point increases by 0.52^oC

MU #2 The greater the concentration of particles the greater the effect.

Example

Consider the following A, B, and C solutions.

In solution A, 1 mole of solute C₆H₁₂O₆(s) produces 1 mole of particles C₆H₁₂O₆(aq).

In solution B, 1 mole of solute NaCl(s) produces 1 mole of particles Na⁺(aq) and 1 mole of particles Cl^-(aq) or 2 moles of particles.

In solution C, 1 mole of solute CaCl₂(s) produces 1 mole of particles Ca²⁺(aq) and 2 moles of particles Cl^-(aq) or 3 moles of particles.

TEST YOUR UNDERSTANDING

1.  As a solute is added to a solvent, what happens to the freezing point and the boiling point of the solution?

(1) The freezing point decreases and the boiling point decreases.

(2) The freezing point decreases and the boiling point increases.

(3) The freezing point increases and the boiling point decreases.

(4) The freezing point increases and the boiling point increases.

2.  A 2.0-molal sugar solution has approximately the same freezing point as a 1.0-molal solution of

(1) CaCl₂              (2) CH₃COOH                     (3) C₂H₅OH             (4) NaCl

3. Dissolving 1 mole of KCl in 1,000 grams of H₂O affects

            1. the boiling point of the H₂O, only       3. both the boiling point and the freezing point of the H₂O         

            2. the freezing point of the H₂O, only    4. neither the boiling point nor the freezing point of the H₂O

1/03

What occurs when NaCl(s) is added to water?

(1) The boiling point of the solution increases, and the freezing point of the solution decreases.

(2) The boiling point of the solution increases, and the freezing point of the solution increases.

(3) The boiling point of the solution decreases, and the freezing point of the solution decreases.

                (4) The boiling point of the solution decreases, and the freezing point of the solution increases.

1/04

13 Compared to pure water, an aqueous solution of calcium chloride has a
    (1) higher boiling point and higher freezing point (2) higher boiling point and lower freezing point
    (3) lower boiling point and higher freezing point (4) lower boiling point and lower freezing point

1/06

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