An equilibrium was established after 0.100 mol of hydrogen gas and 0.100mol of iodine gas were added to an empty 1.00L reaction vessel and heated to 700K. The color intensity of the mixture changed from deep purple to a lighter purple color. At equilibrium, concentration of iodine was 0.0213 mol/L.

Question

Calculate the equilibrium concentrations of hydrogen gas and hydrogen iodide gas as well as Kc.

Answer 1

Start with an equation

H2 + I2 -> 2HI

so 2 moles of HI formed for each mole of I2 used.

at start

0.100 M/L (H2) and 0.100 M/L (I2)

at equilibrium

0.0213 M/L (I2) so 0.0787 M/L I2 used

so 0.1574 M/L HI formed

and 0.0213 M/L equlibrium concentration of H2

Kc=[HI]^2/[H2][I2]

plug in the values and find Kc

Note that this Kc has no units.