Consider the following reaction ,
`Fe^(3+) (aq) + SCN^(-) (aq) hArr [Fe (SCN)]^(2+) (aq)`
A solution is made with initial `Fe^(3+) , SCN^(-)` concentration of `1 xx 10^(-3) M` and `8 xx 10^(-4) M` respectively . At equilibrium `[Fe(SCN)]^(2-)` concentration is `2 xx 10^(-4) M` . Calculate the value of equilibrium constant.

Explanation

`K_(eq) = ([Fe (SCN)]^(2+))/([Fe^(3+)] [SCN^(-)]) = (2 xx 10^(-4) M)/(8 xx 10^(-4) M xx 6 xx 10^(-4) M) = 0.0416 xx 10^(4)`
`K_(eq) = 4.16 xx 10^(2) M^(-1)`