Chapter 14, Problem 53A

Interpretation Introduction

Interpretation:

After finding out the substance with larger vapor pressure, the reason has to be explained.

Concept Introduction:

The vapour pressure of a liquid is directly related to the intermolecular forces of attraction between the particles in liquid. The intermolecular forces of attraction can be H-bonding, dipole-dipole interaction and London dispersion forces. When the intermolecular forces of attraction between two molecules are very high, the vapor pressure of the compound will be lower. When the intermolecular forces of attraction between two molecules are low, the vapor pressure of the compound will be high. The boiling point of a compound also depends on intermolecular attractive forces between two molecules.

Answer to Problem 53A

The vapour pressure of diethyl ether is much higher than butanol.

Explanation of Solution

The intermolecular forces of attraction between butanol molecules are very high due to the presence of strong hydrogen bonding between oxygen and hydrogen atoms. Butanol molecules also exhibit dipole-dipole interaction and London dispersion forces. Butanol molecules are tightly held together by H-bonding between butanol molecules. But there is no such interactions present between diethyl ether molecules. As intermolecular forces of attraction are weaker in diethyl ether, the diethyl ether molecules can easily escape from the surface. So, the vapour pressure of diethyl ether will be much higher than 1-butanol.