Question

Heating 1.0 mole of ammonia and 1.0 mole of molecular nitrogen at 723k in a 10L flask,the following equilibrium is observed:
N2(g)+3H2(g)=2NH3(g)
when the equilibrium is reached ,0.40 moles of molecular hydrogen are present in the flask,determine Kp and Kc and equilibrium composition of the mixture.

Answer 1

initial (N2) = 1/10 = 0.1
initial (H2) = 1/10 = 0.1
equilibrium (H2) = 0.4/10 = 0.04

.......N2 + 3H2 ==> 2NH3
I.....0.1..0.1......0
C.....-x....-3x.....+2x
E..0.1-x...0.1-3x...2x

The problem tells that 0.1-3x = 0.04 so x = 0.02. That allows you to calculate composition of each component. Plug values of each component into Kc expression and solve for Kc.

Plug Kc into Kp = Kc(RT)^delta n and solve for Kp.