Question

Why does CH₄ have a lower boiling point than SiH₄?

A. SiH₄ is a smaller molecule

B. CH₄ has stronger intermolecular forces

C. SiH₄ is a larger molecule

D. CH₄ has weaker intermolecular forces

Answer 1

The boiling point of CH₄ is lower than that of SiH₄ because of the difference in molar mass.

Step-by-step explanation:

Applying the skills acquired in the chapter on chemical bonding and molecular geometry, all of these compounds are predicted to be nonpolar, so they may experience only dispersion forces: the smaller the molecule, the less polarizable and the weaker the dispersion forces; the larger the molecule, the larger the dispersion forces. The molar masses of CH4, SiH4, GeH4, and SnH4 are approximately 16 g/mol, 32 g/mol 77 g/mol and 123 g/mol respectively. Therefore, CH4 is expected to have the lowest boiling point and SnH4 the highest boiling point.