Comparison of boiling points
Molecular mass has NO pertinence to BP, water and ammonia.  Look up the BP of perfluorocyclohexane, hexafluorobenzene, and the hydrocarbons.  If I want to volatize iron, ferrocene.  If I want to volatize iron more, $\ce{Fe(hfac)_3}$ where the ligand is the bidentate enolate anion of 1,1,1,5,5,5-hexafluoro-2,4-pentanedione.  Big MW.  What are the MW and BP of $\ce{UF_6}$?  $\ce{-Si(CH3)_3}$ also confers volatility.

Boiling points are more about polarizability, intermolecular van der Waals and such. Bigger molecules are overall electronically floppy.  Benzene, toluene, xylenes – nice BP steps, but not because of MW. Look up $\ce{SF_6}$ bp.  $\ce{I(CF3)_7}$ boils near 0 °C.  Calculate that MW, and its vapor’s mass/liter at STP compared to dry air at 29 g/liter.