Answer:
Cu₃(PO₄)₂(s), RbNO₃(aq)
Explanation:
This reaction looks like a possible <em>double replacement reaction</em>, in which the metal ions have exchanged partners.
3Cu(NO₃)₂(aq) + 2Rb₃PO₄(aq) ⟶ Cu₃(PO₄)₂ + 6RbNO₃
You must recall the pertinent <em>solubility rules</em>:
1. Salts of Group 1 elements (e.g., Rb⁺) are soluble.
2. Salts containing nitrate ions (NO₃⁻) are soluble.
3. Most salts containing phosphate ions (PO₄³⁻) are insoluble
According to Rules 1 and 1, RbNO₃ is soluble.
According to Rule 3, Cu₃(PO₄)₂ is insoluble.
∴ 3Cu(NO₃)₂(aq) + 2Rb₃PO₄(aq) ⟶ Cu₃(PO₄)₂(s) + 6RbNO₃(aq)