What is the formula of the precipitate that forms when aqueous ammonium phosphate (NH4)3PO4 and aqueous copper(II) chloride are mixed? Group of answer choices Cu3(PO4)2 Cu(NH4)2 Cu3P2 Cu2Cl3
The Correct Answer and Explanation is:
Correct Answer: Cu₃(PO₄)₂
Explanation:
When aqueous ammonium phosphate (NH4)3PO4(NH_4)_3PO_4(NH4)3PO4 and copper(II) chloride CuCl2\mathrm{CuCl_2}CuCl2 are mixed, a double displacement reaction occurs. In this reaction, the positive ions (cations) and negative ions (anions) from both compounds switch partners, potentially forming a precipitate if an insoluble product results.
Step 1: Identify the ions present
- Ammonium phosphate (NH4)3PO4(NH_4)_3PO_4(NH4)3PO4 dissociates into:
- 3 Ammonium ions (NH4+)(NH_4^+)(NH4+)
- 1 Phosphate ion (PO43−)(PO_4^{3-})(PO43−)
- Copper(II) chloride CuCl2\mathrm{CuCl_2}CuCl2 dissociates into:
- 1 Copper(II) ion (Cu2+)(Cu^{2+})(Cu2+)
- 2 Chloride ions (Cl−)(Cl^-)(Cl−)
Step 2: Predict the products
- The copper(II) ions (Cu2+)(Cu^{2+})(Cu2+) will combine with phosphate ions (PO43−)(PO_4^{3-})(PO43−)
- The ammonium ions (NH4+)(NH_4^+)(NH4+) will combine with chloride ions (Cl−)(Cl^-)(Cl−)
The precipitate forms if one of the products is insoluble in water. According to solubility rules:
- Most phosphates (PO43−)(PO_4^{3-})(PO43−) are insoluble, except those with ammonium or alkali metals
- Copper(II) phosphate (Cu3(PO4)2)(Cu_3(PO_4)_2)(Cu3(PO4)2) is insoluble, forming a solid precipitate
- Ammonium chloride (NH4Cl)(NH_4Cl)(NH4Cl) is soluble and remains in solution
Step 3: Write the balanced molecular equation2(NH4)3PO4(aq)+3CuCl2(aq)→Cu3(PO4)2(s)+6NH4Cl(aq)2(NH_4)_3PO_4(aq) + 3CuCl_2(aq) \rightarrow Cu_3(PO_4)_2(s) + 6NH_4Cl(aq)2(NH4)3PO4(aq)+3CuCl2(aq)→Cu3(PO4)2(s)+6NH4Cl(aq)
Step 4: Determine the precipitate formula
The formula of the precipitate is copper(II) phosphate, written as:Cu3(PO4)2Cu_3(PO_4)_2Cu3(PO4)2
Thus, the correct answer is Cu₃(PO₄)₂. The other options:
- Cu(NH₄)₂ is incorrect because copper does not form this compound in the given reaction
- Cu₃P₂ is incorrect, it represents copper phosphide, not relevant here
- Cu₂Cl₃ is incorrect as copper chloride typically forms as CuCl or CuCl₂
Therefore, Cu₃(PO₄)₂ is the correct precipitate formed.
