Answer:
1.125 x 10⁻³.
Explanation:
Kc = [NOCl]²/[NO]²[Cl₂],
Where, [NOCl], [NO], and [Cl₂] is the equilibrium concentration of NOCl, NO, and Cl₂.
∵ Initial concentration of NO and Cl₂ = 0.50 M.
And the equilibrium concentration of NOCl = 0.30 M.
∴ The equilibrium concentration of NO, and Cl₂: [NO] = [Cl₂] = 0.50 M - 0.30 M = 0.20 M.
∴ Kc = [NOCl]²/[NO]²[Cl₂] = [0.30]²/[0.20]²[0.20] = 1.125 x 10⁻³.