What is the chemical formula for copper(II) phosphate?
A) Cu2P
B) Cu2PO4
C) Cu3P2
D) Cu3(PO4)2
The correct answer and explanation is :
The correct answer is:
D) Cu₃(PO₄)₂
Explanation:
Understanding Copper(II) Phosphate Composition
- Copper(II) Ion (Cu²⁺):
- The oxidation state of copper in copper(II) phosphate is +2, meaning each Cu ion has a charge of +2.
- Phosphate Ion (PO₄³⁻):
- The phosphate ion is a polyatomic ion with a charge of -3.
Balancing Charges to Form a Neutral Compound
- The total charge of the compound must be neutral.
- Since Cu²⁺ has a charge of +2, and PO₄³⁻ has a charge of -3, we must find the correct ratio of these ions so that the overall charge sums to zero.
Using the least common multiple (LCM) of the charges:
- The LCM of 2 (for Cu²⁺) and 3 (for PO₄³⁻) is 6.
- To balance, we need 3 Cu²⁺ ions (which gives a total charge of +6) and 2 PO₄³⁻ ions (which gives a total charge of -6).
- Thus, the chemical formula of copper(II) phosphate is Cu₃(PO₄)₂.
Why the Other Options Are Incorrect
- A) Cu₂P:
- Phosphorus alone (P) is not a phosphate ion (PO₄³⁻), and Cu₂P would imply a different compound (copper(I) phosphide).
- B) Cu₂PO₄:
- The charge balance does not work: Cu₂ (2 × +2 = +4) does not balance with PO₄³⁻ (-3 charge).
- C) Cu₃P₂:
- This formula represents copper phosphide, not copper(II) phosphate.
Thus, D) Cu₃(PO₄)₂ is the correct answer.