Chapter 23, Problem 2STP

Interpretation Introduction

Interpretation: To list the compounds in the increasing order of their boiling points.

Concept Introduction: Several factors affect the boiling point apart from the molar mass. The other factors that affect the boiling point are pressure, the effect of impurities, and intermolecular forces. When the compounds have similar molar mass then all the other factors play a role in determining the boiling point of a compound.

Answer to Problem 2STP

Ethane, methanal, and methanol. Option A

Explanation of Solution

The boiling point of the given compounds with similar molar mass is affected by the intermolecular forces that exist in the molecule. Alkanes that are ethane will have only van der Waal’s force of attraction. Aldehydes like methanal will have dipole-dipole interactions and the alcohols will have hydrogen bonding as well as London-dispersion forces also. The weaker the intermolecular forces lower will be the boiling point. Hence, alcohols will have a higher boiling point than aldehydes and alkanes.

Conclusion

Hydrogen bonding will be stronger than the dipole-dipole interactions and van der Waal forces of attraction. Therefore, alcohols that have hydrogen bonding in them will have the highest boiling point and the alkanes with van der Waal’s forces of attraction which are weak have the lowest boiling points.