Chapter 16.3, Problem 33LC

Interpretation Introduction

Interpretation: To determine that only non-volatile solutes cause the elevation of the solvent’s boiling point.

Concept introduction: Non-volatile solutes are those solutes that do not form vapor at room temperature.

The boiling point of elevation is directly proportional to that of the molality of the solute particles, in a dilute solution with a non-volatile solute.

Answer to Problem 33LC

For non-volatile solutes, the boiling point elevation occurs because more energy is required to reach the boiling point temperature.

Explanation of Solution

Boiling point of elevation

The boiling point of elevation is directly proportional to that of the molality of the solute particles, in a dilute solution with a non-volatile solute.

  $\Delta T_b=K_{b}m$

Where,

• $\Delta T_b$ represents the amount through which the boiling point is raised.
• $m$ represents molality (the moles of solute particles).
• $K_b$ represents the molal boiling point elevation constant that depends on the solvent.

For Non-volatile solution

• Solvation shells are formed around those solute particles present in a Non-volatile solute solution.
• Solvation shells mean the polar ends of the water around the solute.
• As the shells are present so there is fewer water molecule having sufficient kinetic energy to escape from the solution causing lower vapor pressure.
• Freezing point depression occurs, disrupting the hydrogen bond ice structure.
• Boiling point elevation is observed as more energy is required to reach the boiling point temperature.

Conclusion

For non-volatile solutes the boiling point elevation occurs, because more energy is required to reach the boiling point temperature.