Question

If a sample of gas which weighs 0.400 g has a volume of 250 mL at STP, what is the molecular weight of the gas?

Answer 1

Approx. `36.0*g*mol^-1`

Explanation:

The molar volume of an Ideal Gas at `STP` is `22.4*L*mol^-1`.

We assume that the gas behaves ideally, and thus we multiply the given density `(g*L^-1)` by the molar volume at `STP`, to give....

`(0.400*g)/(0.250*cancelL)xx22.4*cancelL*mol^-1` `=` `35.9*g*mol^-1`.

Given this molecular weight, the gas is quite possiby `HCl`.