Chapter 14, Problem 60A

Interpretation Introduction

Interpretation: The volatility of liquid is to be defined and vapor pressure and intermolecular forces of attractions are to be discussed.

Concept introduction: Volatility of a liquid describes the state of a substance in its vaporized form.

Answer to Problem 60A

A substance that has a measurable vapor pressure and evaporates readily at normal temperature is said to be volatile.

Volatile liquids have large vapor pressure due to the presence of weak intermolecular forces acting between them.

Intermolecular forces exist among the molecules of substance like solid, liquid or gaseous substances. Hydrogen bonding is present in volatile liquids like ethanol i.e. CH₃CH₂OH.

Explanation of Solution

Particles of liquid have sufficient kinetic energy to convert it into gaseous state. This process is called vaporization. On increasing the temperature, a small fraction of particles at the surface, having high kinetic energy is able to break away from the forces of attraction of other particles and gets converted into vapours. Thus, volatile liquids have larger vapour pressure due to the presence of weak intermolecular forces acting between them.

The electronegativity difference between Hydrogen and oxygen atom in case of ethanol results in the displacement of electron towards the more electronegative atom. Due to which oxygen atom acquire slight negative charge and Hydrogen acquire positive charge.

The positively charged H-atom of one molecule make electrostatic force of attraction with negatively charged atom of oxygen molecule and form H-bond.

Conclusion

On increasing the temperature of solids, the kinetic energy of the particles increases i.e. more number of particles get enough kinetic energy to go into the vapour state. Thus, volatile liquids have high vapor pressure.