The compound O3 has van der Waals constants a = 3.570 atm•L2/mol2 and b = 0.0487 L/mol. Using both the ideal gas law and van der Waals's equation, calculate the pressure expected for 12 mol of O3 gas in a 4.00-L container at 20 °C.

 

Ideal gas law

PV = nRT

V = 4 L

n = 12 mol

T = 20 + 273 = 293

P = nRT/V = (12 mol) (0.0821 L atm/mol K) (293 K)/(4 L)

P = 72.1659 atm ~ 72.17 atm

Van der waal's equation

(P + an²/V²) (V-nb) = nRT

P = nRT/(V-nb) - an²/V²

P = (12 mol x 0.0821 L atm/mol K x 293 K)/ (4 L - 12 mol x 0.0487 L/mol) - (3.57 atm L²/mol² x (12 mol)²/(4 L)²)

P = 52.3833 atm ~ 52.38 atm