Final answer:
When excess NH3 is added to CuSO4, it forms a complex ion [Cu(NH3)4]²+ (aq), which increases the solubility of Cu²+.
Step-by-step explanation:
Adding an ionic compound that contains Cu²+ to an aqueous ammonia solution will result in the formation of [Cu(NH3)4]²+ (aq).
This is because NH3 forms a complex ion with Cu²+.
The formation of the complex ion pulls equilibrium towards the right, allowing more Cu²+ to dissolve.