Answer
Please see the work below.
Work Step by Step
We know that yes the heat of vaporization of $0.9$, $5.6$ and $20.4\frac{KJ}{mol}$ for $H_2$, $N_2$ and $Cl_2$ respectively increase in the order of the respective molecular masses of $2.016$, $28.02$ and $71.0$. We also know that the London forces increase in order of increasing molecular mass.
