2 A (aq) + B (aq) ⇌ C (aq) + D (aq) Kc 44.9, [A] = 0.772 M, [B] = 0.0339 M, and [C] = 0.782 M, what is the equilibrium concentration (in M) of D?

Question

Consider the following reaction:

2 A (aq) + B (aq) ⇌  C (aq) + D (aq)

If the Kc for this equilibrium reaction is 44.9, and the equilibrium concentrations of A, B, and C are: [A] = 0.772 M, [B] = 0.0339 M, and [C] = 0.782 M, what is the equilibrium concentration (in M) of D?

Answer 1

2A(aq) + B(aq) <==> C(aq) + D(aq)

Write the equilibrium expression: Kc = [C][D] / [A]²[B]

Put in known values and solve for unknown:

44.9 = (0.782)(D) / (0.772)²(0.0339)

44.9 = 0.782D / 0.0202

D = 1.16 M

(Check the math)