The name of the ionic compound (NH4)3PO4 is
a) ammonium phosphate
b) nitrogen hydrogen phosphate
c) tetrammonium phosphate
d) ammonia posphide
e) triammonium phosphate
The correct answer and explanation is :
The correct answer is:
a) ammonium phosphate
Explanation:
The given chemical formula (NH₄)₃PO₄ consists of two ions:
- Ammonium ion (NH₄⁺)
- Phosphate ion (PO₄³⁻)
To systematically determine the name of the compound, follow these steps:
Step 1: Identify the Cation and Anion
- NH₄⁺ (Ammonium ion): A polyatomic ion with a +1 charge.
- PO₄³⁻ (Phosphate ion): A polyatomic ion with a -3 charge.
Step 2: Charge Balancing
Each ammonium ion (NH₄⁺) carries a +1 charge, and the phosphate ion (PO₄³⁻) has a -3 charge. To balance the charges, three NH₄⁺ ions are required for every PO₄³⁻ ion:
[
(3 \times +1) + (-3) = 0
]
This ensures a neutral compound, leading to the formula (NH₄)₃PO₄.
Step 3: Naming the Compound
- The NH₄⁺ ion is named ammonium.
- The PO₄³⁻ ion is named phosphate.
Since this is an ionic compound, no prefixes (such as mono-, di-, tri-) are needed. The name follows the standard naming convention of ionic compounds:
Cation name + Anion name = Ammonium phosphate
Why Other Options Are Incorrect:
- b) Nitrogen hydrogen phosphate → This does not correctly describe the ionic components.
- c) Tetrammonium phosphate → Incorrect prefix; ammonium ions are not counted with prefixes.
- d) Ammonia phosphide → Ammonia (NH₃) is a molecule, not an ion, and phosphide (P³⁻) is different from phosphate (PO₄³⁻).
- e) Triammonium phosphate → “Triammonium” is not a standard nomenclature term in ionic chemistry.
Thus, the correct name for (NH₄)₃PO₄ is ammonium phosphate.