When 1 mole of $H_2\left(g\right)$ and 3 moles of $I_2$ vapours are allowed to react x moles of $HI\left(g\right)$ is formed at equilibrium. Addition of a further 2 moles of $H_2\left(g\right)$ gave an additional x moles of $HI\left(g\right)$ at new equilibrium. The value of equilibrium constant for the reaction $H_2\left(g\right)+I_2\left(g\right)\rightleftharpoons 2HI\left(g\right)$ is