Question

The density (in g/L) of helium (He) gas at 723 torr and 225 K is?

How many g/L ?

Answer 1

`rho=0.2*g*L^-1`

Explanation:

Now `PV=nRT`.....and thus `P/(RT)=n/V=("mass"/"molar mass")/V`

And so `P/(RT)xx"molar mass"="mass"/V=rho_"helium"` as required...

ANd we assume of molar quantity of `1*mol` under the given conditions....

`rho_"helium"=((723*"Torr")/(760*"Torr"*atm^-1)xx4.003*g*mol^-1)/(0.0821(L*atm)/(K*mol)xx225*K)`

`=0.206*g*L^-1`