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
x--------------------------------170.0 liters
s=(1 mol * 170.0 liters ) / 22.4 liters≈7.59 moles
2) we calculate the mass of this amount of gas.
32 g-------------------------1 mol
x------------------------------ 7.59 moles
x=(32 g * 7.59 moles) / 1 mol=242.86 g.
Answer: the mass of gas in the tank (T=273ºK and P=1 atm) is:
242.86 g.