At 700 K, equilibrium constant for the reaction:

H2 (g) + I2 (g) 2HI (g)


is 54.8. If 0.5 mol L–1 of HI(g) is present at equilibrium at 700 K, what are the concentration of H2(g) and I2(g) assuming that we initially started with HI(g) and allowed it to reach equilibrium at 700K?

For the reaction,

H2 (g) + I2 (g) 2HI (g)


Equilibrium constant is given to be 54.8.


i.e, Kc =


Let x be equilibrium concentration of H2 at equilibrium. Then equilibrium concentration of I2 will also be x. Since, initially there was only HI present, equal amount of H2 and I2 will be produced.


At equilibrium:


Kc =


= = 54.8


x =


= 0.0675


Therefore, concentration of H2 and I2 is 0.0675 mol L-1


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