Assuming ideal gas, we can use the equation:
PV = nRT
n = PV / RT = (1.0 atm) × (1.65 × 10^5 ft^3 × 28.32 L/ft^3) / ((0.08205 L atm / K mol) × (25 + 273) K)
n = 191013.382 mol He
(191013.382 mol He) x (4.00g He/mol) = 764053.53 g = 764 kg He
Hope this helps.
