Which of the following equilibrium expressions corresponds to a heterogeneous equilibrium?(a) Kc =[NH4+][OH−][NH3](b) Kc =[H+][C2H3O2−][HC2H3O2](c) Kc =[Ag(NH3)2+][Cl−][NH3]2(d) Kc = [Ba2+][F−]2

c.

d.

Explanation:

An heterogeneous equilibrium is defined as a system whose reactants, products, or both are in more than one phase.

Also, you must know in an equilibrium constant you don't take solids or pure liquids. Thus:

a.

The reaction must be: NH₃(aq) + H₂O(l) ⇆ NH₄⁺(aq) + OH⁻(aq)  All reactants are in the same phase.

b.

The reaction must be: HC₂H₃O₂(aq) ⇄ H⁺(aq) + C₂H₃O₂⁻(aq)  All reactants are in the same phase.

c.

The reaction must be:  2NH₃(aq) + AgCl(s) ⇄ Ag(NH₃)₂⁺(aq) + Cl⁻(aq)

Reactants aren´t in the same phase. Heterogeneous equilibrium

d.

The reaction must be: BaF₂(s) ⇆ Ba²⁺(aq) + 2F⁻(aq)

Reactants aren´t in the same phase. Heterogeneous equilibrium

I hope it helps!