Chapter 14, Problem 29A

Interpretation Introduction

Interpretation: The forces that account for the higher boiling point of water than ammonia has to be determined.

Concept introduction: The temperature at which the liquid’s vapour pressure becomes equal to pressure of atmosphere is called boiling point. Boiling point depends on the bonding between molecules which keep them together. Intermolecular forces are of various types such as van der waals, hydrogen bonding, dipole interaction and London dispersion.

Answer to Problem 29A

The force that account for higher boiling point of water than ammonia is the stronger hydrogen bonding among water molecules than ammonia.

Explanation of Solution

Polar molecules that have elements that are high in electro negativity like nitrogen, oxygen and fluorine directly attached to hydrogen atom, exhibit hydrogen bonding. They are held together by hydrogen bonding between molecules.

Hydrogen bonding is a special kind of dipole-dipole bond.

Since oxygen is higher in electro negativity than nitrogen therefore the hydrogen bonding formed between water molecules are stronger than between ammonia molecules.

Conclusion

The force that account for higher boiling point of water than ammonia is the stronger hydrogen bonding among water molecules than ammonia.