An equilibrium mixture of the reaction  $2H_{2}S\left(g\right)\rightleftharpoons 2H_2\left(g\right)+S_2\left(g\right)$    had 0.5 mole  $H_{2}S$, 0.10 mole $H_2$   and 0.4 mole $S_2$   in one litre vessel.  The value of equilibrium constant (K) in mol  $litr{e}^{-1}$  is  $x\times {10}^{-3}$     then  x is