$2NOC{l}_{\left(g\right)}\rightleftharpoons 2N{O}_{\left(g\right)}+C{l}_{2\left(g\right)}$

In an experiment, 2.0 moles of NOCl was placed in a one – liter flask and the concentration of NO after equilibrium established was found to be 0.4 mol/L. The equilibrium constant at ${27}^{o}C$ is _____$\times {10}^{-4}.$

$\left(125\times {10}^{-4}\right)$

                                      $2NOCl\rightleftharpoons 2NO+C{l}_2$

Initially                            2 mol            0          0
At Equilibrium                 2-0.4          0.4       0.2 = 1.6
$K_C=\frac{{\left[NO\right]}^2\left[C{l}_2\right]}{{\left[NOCl\right]}^2}=\frac{{\left(0.4\right)}^2\left(0.2\right)}{{\left(1.6\right)}^2}=0.0125=125\times {10}^{-4}$