Question

Calculate the density of Argon (Ar) gas at 400.0K and 1.23 atm.

Answer 1

P*molar mass = density*RT
density will be in g/L.

Answer 2

what is p and what is RT

Answer 3

Aw C'mon. P is pressure in atm, R is the gas constant in L and atm, T is kelvin temperature.
This is just a rearrangement of PV = nRT.