Consider the following reaction:

Question

2 HI (g) → H2 (g) + I2 (g)
Assume that an experiment is carried out in which the starting concentration of HI (g) is 0.100 mol/L. No
products are present at the beginning of the reaction. When equilibrium is established, the concentration of
H2 (g) is 1.41 x 10-2 mol/L. Calculate the equilibrium constant for the above reaction.

Answer 1

.................2 HI (g) → H2 (g) + I2 (g)
I................0.1.............0...........0
C.............-2x..............x...........x
E...........0.1-2x...........x...........x

Write the expression for Kc, substitute the E line from the above, substitute 1.41E-2 for H2 and I2 . evaluate 0.1-2x and solve for Kc.