The ideal gas law relates the pressure (P), volume (V), number of moles (n), and temperature (T) of a given ideal gas through the equation,
PV = nRT
If we are to determine the volume of the gas, we derive the equation such that it takes the form of,
V = nRT/P
Substituting,
V = (0.425 mol)(0.0821 L.atm/mol.K)(900 + 273 K) / 3 atm
V = 13.64 L
Thus, the volume of the ideal gas is approximately 13.64 L.