In: Chemistry
Calculating Equilibrium Constants
The following reaction was performed in a sealed vessel at 752
∘C :
H2(g)+I2(g)⇌2HI(g)
Initially, only H2 and I2 were present at concentrations of
[H2]=3.75M and [I2]=3.00M. The equilibrium concentration of I2 is
0.0900 M . What is the equilibrium constant, Kc, for the reaction
at this temperature?
H2(g) + I2(g) ⇌ 2HI(g)
Initial 3.75 M 3.00 M 0
at equilibrium 3.75- x 3-x 2 x
So,
equilibrium concentration of I2 = 3-x
But given that equilibrium concentration of I2 = 0.0900 M
Then,
3-x = 0.09
x = 2.91 M
Therefore, equilibrium concentrations are
[H2] = 3-75 -x = 3.75 - 2.91 = 0.84 M
[I2] = 0.09 M
[HI]= 2 x= 2 x 2.91 = 5.82 M
Kc = [HI]2/ [H2] [I2]
= (5.82)2 / (0.84) (0.09)
= 448.05
Therefore, equilibrium constant Kc = 448.05