The value of keq for the equilibrium h2 (g) + i2 (g) 2hi (g) is 794 at 25 °c. what is the value of keq for the equilibrium below? 1/2 h2 (g) + 1/2 i2 (g) hi (g)

The formula for Keq for the first chemical reaction with given Keq is:

Keq 1 = [ HI ]^2 / [ H2 ] [ I2 ]

While the formula for Keq for the 2nd is:

Keq 2 = [ HI ] / [ H2 ]^ (1/2) [ I2 ]^ (1/2)

We can see that the coefficients in the reaction are equal to the exponents in the equilibrium equation. Therefore if we divide the whole reaction by 2, then that means we have to take the square root of the equilibrium equation. Or in this case,

Keq 2 = sqrt (Keq 1)

Keq 2 = sqrt (794)

Keq 2 = 28.19