To find out the equilibrium constant (K) of a reaction, it is compulsory to mention the balanced equation of the reaction-why?

Explanation

The value of equilibrium constant (K) depends on how the balanced equation of the reaction is written, e.g., the formation of HI (g) from `H_(2)(g) and I_(2)(g)` can be written in two different ways:
(1) `H_(2)(g)+I_(2)(g)hArr 2HI(g)`
(2) `(1)/(2)H_(2)(g) +(1)/(2)I_(2)(g) hArr HI(g)`
both (1) and (2) express the same reaction but the coeffcients of reactants and products are different. as a result, the value of equilibrium constant (K) for the reaction will not be the same in the above two cases.