Question

Write the chemical reaction that occurs between aqueous ammonia and solid copper(II) phosphate?

The copper(II) ion reacts with phosphate ion to form an insoluble ionic compound, Ksp = 1.40×10^–37. The copper(II) ion also forms a complex ion with ammonia, [Cu(NH3)4]2+, Kf = 5.03×10^13.

Answer 1

`Cu_3(PO_4)_2(s) rightleftharpoons 3Cu^(2+)(aq)+2PO_4^(3-)(aq)`
`Cu^(2+)(aq)+4NH_3(aq)rightleftharpoonsCu(NH_3)_4^(2+)(aq)`
`---------------`
`Cu_3(PO_4)_2(s)+4NH_3(aq)rightleftharpoons 2Cu^(2+)(aq)+2PO_4^(3-)(aq)+Cu(NH_3)_4^(2+)(aq)`

The bottom equation are the two equilibra interacting.

We may find the equilibrium constant by using the previous two.

`K_(sp)*K_f approx 7.04*10^-23`

The salt is still very insoluble, but the `NH_3` in the solution is helping, since the constant increased in magnitude.