Answer:
Kc = 0.0216
Explanation:
To do this, we need to write the equilibrium reaction which is the following:
NH3 + O2 <------> N2O4 + H2O
And now, let's balance the equation
4NH3 + 7O2 <--------> 2N2O4 + 6H2O
The general expression for Kc is:
Kc = [N2O4]²[H2O]⁶ / [O2]⁷[NH3]⁴
Now, in order to know the concentrations, we need to do an ICE chart here, so we can know the final concentrations of all species here:
4NH3 + 7O2 <--------> 2N2O4 + 6H2O
I: 3.6 3.6 0 0
C: -4x -7x +2x +6x
E: 3.6 - 4x 3.6 - 7x 0.6 +6x
According to this, we know that N2O4 is 0.6M, but in the change we have that it gained 2x so the value of x will be:
2x = 0.6
x = 0.6/2 = 0.3
Therefore, the value of x is 0.3 ans we can know now the concentrations of all species in equilibrium, and then, the kc:
[NH3] = 3.6 - 4(0.3) = 2.4 M
[O2] = 3.6 - 7(0.3) = 1.5 M
[H2O] = 6(0.3) = 1.8 M
Now the value of Kc would be:
Kc = (0.6)² (1.8)⁶ / (2.4)⁴ (1.5)⁷
Kc = 0.0216
