What is the k expression for this reaction? plz help !

K = [HI]² / [H₂] [I₂]

Explanation:

To write the expression of equilibrium constant, K, it is important that we know how to obtain the equilibrium constant.

The equilibrium constant, K for a given reaction is simply defined as the ratio of the concentration of the products raised to their coefficient to the concentration of the reactants raised to their coefficient. Thus, the equilibrium constant is written as follow:

K = [Product] / [Reactant]

Now, we shall determine the equilibrium constant for the reaction given in the question above. This can be obtained as illustrated below:

H₂(g) + I₂(g) —> 2HI (g)

K = [HI]² / [H₂] [I₂]