In the molecular weight determination experiment, what would be the effect if some air remains in the flask after the compound was completely vaporized?

Answer 1

The molecular weight of the compound would be some kind of a weighted average between the compound and the air that was left.

Answer 2

Not certain of your procedure, however if you were measuring volume, and air were incuded, then your moles calcuated would be too high, and so the mol mass too low.