Question

For the following: 4NH_3(g) + 3O_2(g)--> 2N_2(g) + 6H₂O_(g) with K=1E-8

All Reactants are initially at 12M and you have no products. Calculate the equilibrium concentration of  O_2(g)

O_2(g) M

Answer 1

Let 3x M represents the change in the concentration of oxygen.

Initial concentration (M)	12	12	0	0
Equilibrium concentration (M)	12-4x	12-3x	2x	6x

The expression for the equilibrium constant is

Substittue values in the above expression.

But since the value of equilibrium constant is very small, x is also very small in comparision to 12 M.

Hence, and

Hence, the expression for the equilibrium constant becomes

Hence, the equilibrium oxygen concentration is 11.6 M.