The reaction $N_2+3H_2$to 2N$2N{H}_3$ takes place at 450C. 1 mole of $N_2$ and 2 moles of $H_2$ are mixed in a 1 litre vessel and 1 mole of $N{H}_3$ is formed at equilibrium. Then $K_C$ for the above reaction is

$K_C$ is equilibrium constant formed by the formula for the reaction for the ratio of the concentration of product and reactants.

                   2$\alpha$ = 1

                    $\alpha$ = ½

            $K_c=\frac{1X1}{\frac{1}{2}X\frac{1}{2}X\frac{1}{2}X\frac{1}{2}}$

                  = 16

Hence, the correct answer is option (C) 16.