In this question, we have to use the Ideal gas Law formula in order to find the missing volume, for this formula we have:
PV = nRT
We have:
P = 1.0 atm
V = ?
n = 3.2 moles
R is the gas constant = 0.082
T = 25°C, but we need it in Kelvin, 298 K
Now adding these values into the formula:
1 * V = 3.2 * 0.082 * 298
V = 78.2 Liters of Volume