Which represents the correct equilibrium constant expression for the reaction below?

Upper C u (s) plus 2 upper A g superscript plus (a q) double-headed arrow upper C u superscript 2 plus (a q) plus 2 upper A g (s).

Explanation:

1. Chemical equilibrium equation:

2. Species

In an equilibrium constant expression you do not include the solid substances; only gases and dissolved substances.

The symbol means solid, thus Cu(s) and Ag(s) shall not appear in your equilibrium constant expression.

The symbol means in aqueous solution, thus the both and must appear in the equilibrium constant expression.

3. Equilibrium constant expression.

It is the quotient of the product of the concentrations of the species on the right hand side of the equilibrium equation, each raised to its corresponding coefficient, and the product of the concentrations of the species on the left hand side, each raised to its coresponding coefficient.

"among the transition metal elements, manganese and zinc have a slight lowering of electronegativities. the reason behind this is that the nuclear charges of these elements are slightly weaker than the other transition metal elements due to the way their valence electrons are filled up. both manganese and zinc have their valence electrons filled up to the 4th shell with 1 pair of electrons (4s2) completely occupying it. although the electrons in the 3rd shell (3d) are yet to be paired since the outer most shell is filled up, the ability of the nucleus to attract electrons is lessened. hence,   the electronegativity (or the ability to attract electrons) is lessened."