$t =0 \quad\quad 2 M \quad\quad\quad\quad\quad -\quad\quad\quad\quad -$

$t = t _{ eq }\quad(2- x ) M\quad\quad\quad\quad xM \quad\quad \frac{ x }{2} M$

$\because x =0.4 \,M$

$\therefore[ NOCl ]_{ eq }=1.6\, M$

${[ NO ]_{ eq }=0.4 \,M }$

${\left[ Cl _{2}\right]_{ eq }=0.2 \,M }$

$\Rightarrow K _{ c }=\frac{[ NO ]^{2}\left[ Cl _{2}\right]}{[ NOCl ]^{2}}=\frac{[0.4]^{2}[0.2]}{[1.6]^{2}}$

$K _{ c }=\frac{32}{2.56} \times 10^{-3}$

$K _{ c }=12.5 \times 10^{-3}$

$K _{ c }=125 \times 10^{-4}$