Combine these two equilibrium reactions, into a single reaction equation that shows the overall equilibrium.

Question

A (g) + B (g)  C(g)      fast equilibrium

 B (g) + C (g)  D(g)      fast equilibrium

Which of the following expressions is the correct equilibrium-constant expression for the overall equilibrium?

A.

B. [B]2[C][A]
C.
D.

E.

Answer 1

A (g) + B (g) <==> C(g)      fast equilibrium

 B (g) + C (g) <==> D(g)      fast equilibrium

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A + B + B + C <==> C + D combined

A + 2B <==> D combined simplified

K = [D] / [A][B]²

Answer 2

Answer is C.

K_eq = k[Products]^coefficient/[Reactants]^coefficient

since C cancels out upon adding the equations:

K_{eq =} k[D]/[A][B]²