Question

Consider the chemical reaction 2nh3(g) n2(g) + 3h2(g). the equilibrium is to be established in a 1.0 l container at 1,000 k, where kc = 4.0 Ã 10â2. initially, 1,220 moles of nh3(g) are present. estimate the equilibrium concentration of h2(g). show all your work

Answer 1

We are given the chemical reaction:

2NH3(g) = N2(g) + 3H2(g)

To determine the equilibrium concentration of hydrogen gas, we use the equation above, the Kc that is given, initiall moles of NH3 and the volume of the system. The equilibrium constant is equal to the ratio of the product of the equilibrium concentrations of the products and the equilibrium concentration of the reactant. It is expressed as:

Kc = [N2] [H2]^3 / [NH3]^2 = 4.0 x10^-2

We use the ice table:
                NH3             N2              H2
I            1220 / 1           0                 0
C              -2x               +x              +3x
-----------------------------------------------------
E         1220 - 2x          x                  3x

Substituting to the expression of Kc,
4.0 x10^-2 = [x] [3x]^3 / [1220 - 2x]^2

Solving for x, we will have
x =  6.8336 = [N2]
3x = 3(6.8336) = 20.5008 = [H2]

Therefore, the equilibrium concentration of H2 would be 20.50 M.