0.15 mol of CO taken in a 2.5 L flask is maintained at 705 K along with a catalyst so that the following reaction takes place CO(g) + 2H2(g) ⇌ CH3OH(g). Hydrogen is introduced until the total pressure of the system is 8.5 atm at equilibrium and 0.08 mol of methanol is formed. Kp and Kc respectively are:
= 0.045 and = 150.85
Initially there was 0.15 mol of CO (g) and at equilibrium 0.08 mol of CH3OH was formed
CO(g)+2H2(g)⇋CH3OHMoles at star0.15a0Moles at equb.(0.15−x)(a−2x)0.08or(0.15−0.08)(a−0.16)0.08
Total moles at equilibrium =(0.15−0.08)+(a−(2×0.08))+0.08=a−0.01
We can equate the above to n = number of moles at equilibrium from
n = PVRT P = 8.5 atm, R = 0.0821 atmLK−1 mol−1, V = 2.5 litre and T = 705 K
n = 0.3676
No of moles of H2 (g) at equilibrium = n - (0.15-0.08) - 0.08 = 0.2176
Now Kc=[CH3OH][H2]2[CO]= 150.8585 mole−2litre2
Kp much more straightforward once we figure out Kc.
Kp = Kc(RT)Δn
= 150.85 × (0.0821×705)−2 = 0.045atm−2