Question

What is the density of hydrogen gas using the ideal gas law?

Answer 1

And, using standard conditions of $P=1\cdot atm$... and $T=298\cdot K$, we address the Ideal Gas equation ... (at least near standard conditions ...)
$PV=nRT...\frac{n}{V}=\frac{P}{RT}=\frac{\frac{mass}{molarmass}}{V}=\frac{P}{RT}$
And so ...
$\underset{}{density=\rho }\frac{mass}{V}=\frac{P}{RT}\times molarmass$
And thus our working equation... $\rho H_2=\frac{P}{RT}\times 2.016\cdot g\cdot mo{l}^{-1}$
$=\frac{1\cdot atm\times 2.016\cdot g\cdot mo{l}^{-1}}{0.0821\cdot \frac{L\cdot atm}{K\cdot mol}\times 298\cdot K}\cong 0.1\cdot g\cdot L^{-1}$
We note that hydrogen gas, as are all elemental gases with any chemistry, is bimolecular, i.e. $H_2...$