Question

A gas has a density of 1.234g/L at STP

Answer 1

In the case of ideal conditions gas with the density of 1.234 g/L will occupy the volume of 22.4 L. Molecular weight of the gas is:
M = volume x density = 1.234 g/L x 22.4 L = 28.
The gas is N₂ (molecular weight 28).