2 HI(g) H2(g) + I2(g)
The reaction above has an initial concentration of 2.00 M HI. (No other species are initially present.) If 22.4% of the HI has reacted when equilibrium is established, calculate Kc for the reaction.
To calculate the equilibrium constant, Kc, for the reaction, we need to determine the concentrations of the reactants and products at equilibrium.
Given that 22.4% of the initial HI has reacted, we can determine the concentration of HI remaining at equilibrium as:
[H2] = [I2] = 0 (since they are not present initially)
Let x represent the concentration of HI that has reacted at equilibrium, in M. Since 22.4% of the initial HI has reacted, the concentration of HI remaining is (2.00 - 0.224) M.
At equilibrium, the equation can be written as:
2 HI (g) <--> H2 (g) + I2 (g)
The equilibrium concentrations and expression for Kc are:
[HI] = (2.00 - 0.224) M
[H2] = 0 M
[I2] = 0 M
Kc = ([H2] * [I2]) / [HI]^2
Substituting the values into the expression for Kc:
Kc = (0 * 0) / [(2.00 - 0.224)^2]
Since the concentration of H2 and I2 are both 0 M, the numerator becomes 0. The denominator is:
(2.00 - 0.224)^2 = 1.776^2
Kc = 0 / 1.776^2
Kc = 0
Therefore, the equilibrium constant, Kc, for the reaction is 0.