How to write an expression for a given equilibrium reaction equation, in terms of the concentrations of products and reactants?

Question

The copper (ii) ion-tetraamine copper (ii) ion equilibrium may be presented by the equation,

Cu⁺⁺ + 4NH₃ ⇌ [Cu(NH₃)₄]⁺⁺

How do I write an expression for the equilibrium constant of this reaction in terms of the concentrations of products and reactants?

Answer 1

K = [Cu(NH₃)₄]⁺⁺ / [Cu⁺⁺][NH₃]⁴