Question

For the reaction 2NOCl(g) <-----> 2NO(g) + Cl2(g), Kc = 8.0 at a certain temperature. What concentration of NOCl must be put into an empty 4.00 L reaction vessel in order that the equilibrium concentration of NOCl be 1.00 M?

Answer 1

Answer is: concentration of NOCl is 3.52 M.

Balanced chemical reaction: 2NOCl(g) ⇄ 2NO(g) + Cl₂(g).
Kc = 8.0.
[NOCl] = 1.00 M; equilibrium concentration.
[NO] = x.
[Cl₂] = x/2; equilibrium concentration of chlorine.
Kc = [Cl₂] ·[NO]² / [NOCl].
8.00 = x/2 · x² / 1.
x³/2 = 8.
x = ∛16.
x = 2.52 M.
co(NOCl) = [NOCl] + x.
co(NOCl) = 1.00 M + 2.52 M.
co(NOCl) = 3.52 M; the initial concentration of NOCl.