Chapter 12, Problem 12.57P

Interpretation Introduction

Interpretation:

The reason for the higher boiling point of ethylene glycol as compared to propanol and a compound with a similar molar mass is to be determined.

Concept introduction:

Intermolecular forces operate between the molecules so changes with change in the phase and effects with physical properties of the substance. In intermolecular forces, the bond is formed between two molecules with partial charges that are present relatively far away from each other. The types of intermolecular forces are as follows:

1. Ion-dipole: Ion-dipole forces are the attractive forces that exist between an ion and a polar molecule.

2. Hydrogen bond: Hydrogen bonding is the attractive forces that exist between the molecule with a hydrogen atom bonded to an electronegative atom like fluorine, nitrogen, and oxygen of one molecule and an electronegative atom of another molecule.

3. Dipole-dipole: Dipole-dipole is the attractive forces that exist between two polar molecules that have a permanent dipole.

4. Ion-induced dipole: Ion-induced dipole is the attractive forces that exist between the ion and a nonpolar molecule.

5. Dipole-induced dipole: Dipole-induced dipole is the attractive forces that exist between a polar and a nonpolar molecule.

6. Dispersion forces: In dispersion forces, a temporary dipole is generated on one molecule that further induces a temporary dipole on the molecule adjacent to it. The temporary dipole results in the attraction between opposite charges and dispersion forces exist in the molecule. All the atoms and molecules exhibit dispersion forces.

The boiling point of the liquid is defined as the temperature at which the liquid and gas are in equilibrium and the pressure is $1\text{atm}$. The boiling point is directly related to the strength of intermolecular forces. More is the strength of intermolecular forces more will be the boiling point of the compound. The increasing order of strength is as follows:

$\text{dispersion forces}<\text{dipole}-\text{dipole forces}<\text{hydrogen bonds}<\text{ion}-\text{dipole forces}$