Question

what trend in intermolecular forces explains the increase in boiling points of compounds shown in the graph?
the strength of hydrogen bonds increases as molecular weight increases.
the amount of london dispersion forces increases as molecular weight increases.
the polarity of the molecule increases as molecular weight increases.
the dipole forces remain constant as molecular weight increases.

Explanation:

London - dispersion forces are related to molecular size. Larger molecules (higher molecular weight) have more electrons, leading to stronger London - dispersion forces and higher boiling points. These compounds ($CH_4$, $SiH_4$, $GeH_4$, $SnH_4$) do not have hydrogen - bonding or significant changes in polarity in a way that would explain the trend. So, the increase in boiling points is due to the increase in London dispersion forces with increasing molecular weight.

Answer:

The amount of London dispersion forces increases as molecular weight increases.