$9.2 \mathrm{g}$ of ${\mathrm{N}}_2{\mathrm{O}}_4( \mathrm{g})$ is taken in 1 lit vessel and heated. At equilibrium, $50\%$ is dissociated. Equilibrium constant (mol/lit) [MW = 92]

 $9.2 \mathrm{g}$ of ${\mathrm{N}}_2{\mathrm{O}}_4( \mathrm{g})$ is taken in 1 lit vessel and heated. 

${\mathrm{N}}_2{\mathrm{O}}_4( \mathrm{g})\underset{ }{\rightleftharpoons }2N{\mathrm{O}}_2( \mathrm{g})$ At equilibrium, $50\%$ is dissociated.

0.1                        0

0.1-0.05                  2 x 0.05

$K_c=\frac{{\left[N{O}_2\right]}^2}{\left[N_2{O}_4\right]}=\frac{4\times (0.05{)}^2}{0.05}=4\times 0.05=0.2$

Hence the correct option is (B) 0.2