Chapter 15, Problem 29A

Interpretation Introduction

Interpretation: To explain the unusually low vapor pressure of water.

Concept Introduction: Vapor pressure is generally regarded as the tendency of a compound to convert into a gaseous state. This pressure is exerted by the vapor present above the liquid. This vapor pressure is affected by temperature, the concentration of solute, and the nature of the liquid.

Answer to Problem 29A

This is because water is a non-volatile liquid and hence contains low unusual vapor pressure.

Explanation of Solution

There is hydrogen bonding between the water molecules in water. As the intermolecular forces of attraction are strong, the boiling point will increase. Among the intermolecular forces, hydrogen bonding is the strongest intermolecular force and hence, the boiling point will be higher in water. Hence, there is an unusually low vapor pressure of water because it is a non-volatile liquid.

Conclusion

As the boiling point increase, the vapor pressure will decrease. Since there is a hydrogen bonding between the water molecule, it requires more boiling point that is more energy to break which will decrease the vapor pressure.