Consider the following equilibrium, CO(g) + 2H2(g) CH3OH(g) 0.1 mol of CO along with a catalyst is present in a 2 dm3 flask maintained at 500 K. Hydrogen is introduced into the flask until the pressure is 5 bar and 0.04 mol of CH3OH is formed. The Kp is 10-3 (nearest integer). Given : R = 0.08 dm3 bar K-1 mol-1 Assume only methanol is formed as the product and the system follows ideal gas behaviour.
Answer
74
Solution
Total moles at equilibrium:
ntotal = PVRT = 5 20.08 500 = 0.25 mol
CO left = 0.1 - 0.04 = 0.06 mol; CH3OH = 0.04 mol
H2 at equilibrium = 0.25 - 0.06 - 0.04 = 0.15 mol
Partial pressure pi = nintotal P = ni 20 bar
pCO = 1.2 bar, pH2 = 3 bar, pCH3OH = 0.8 bar
Kp = pCH3OHpCO pH22 (pressures in bar, standard pressure 1 bar)
= 0.81.2 32 = 0.810.8
= 0.0741 74 10-3
Answer: 74