Pure ammonia is placed in a vessel at a temperature where its dissociation constant $(\alpha)$ is appreciable. At equilibrium,

• A
  $K_p$ does not change significantly with pressure
• B
  $\alpha$ does not change with pressure
• C
  Concentration of $NH_3$ does not change with pressure
• D
  Concentration of $H_2$ is less than that of $N_2$