Question

If 1.00 L of an unknown gas at STP has a mass of 5.40 g, what is its molar mass?

Answer 1

Approx, `121*g*mol^-1`

Explanation:

The molar volume at `"STP"` is `22.4*L*mol^-1`.

Given this, if we divide the mass by the molar quantity of the gas we get an answer in `g*mol^-1` as required:

`(1.00*L)/(22.4*L*mol^-1)` `=` `0.0446*mol`

`"Molar mass"` `=` `(5.40*g)/(0.0446*mol)` `=` `121*g*mol^-1`