We should indicate first and foremost the assumption of ideal gas behavior so that we can use the ideal gas equation written below:
PV = nRT
For this problem,let's solve for V. Rearranging the equation,
V = nRT/P
Substituting the values,
V = (1 mol)(0.0821 L-atm/mol-K)(30 + 273 K)/1.2 atm
V = 20.73 L of N₂ gas