If the volume of the tank is 170.0 l and the molecular weight of the gas is 32.00 g/mol, what is the mass of gas in the tank

The volume of a mol of any gas is 22.4 liters.
Therefore:
1)We calculate the number of moles :
1 mol 22.4 liters
x170.0 liters

s=(1 mol * 170.0 liters ) / 22.4 liters≈7.59 moles

2) we calculate the mass of this amount of gas.

32 g1 mol
x 7.59 moles

x=(32 g * 7.59 moles) / 1 mol=242.86 g.

the mass of gas in the tank (T=273ºK and P=1 atm) is:
 242.86 g.