. Name the following compounds: Fe3(PO3)2, N3S7, NH3, H2SeO4(aq), MnSO4 · 6H2O
The Correct Answer and Explanation is
Here are the correct names for each compound:
- Fe₃(PO₃)₂ – Iron(II) phosphite
- N₃S₇ – Trinitrogen heptasulfide
- NH₃ – Ammonia
- H₂SeO₄ (aq) – Selenic acid
- MnSO₄ · 6H₂O – Manganese(II) sulfate hexahydrate
Explanation
1. Fe₃(PO₃)₂ – Iron(II) phosphite:
This is an ionic compound composed of iron and the phosphite ion (PO₃³⁻). Iron can have multiple oxidation states, so we determine which is present:
Each PO₃³⁻ has a -3 charge, and there are two of them for a total of -6. To balance this, the total charge from the iron must be +6. With three Fe atoms, each must be +2. Thus, we name it Iron(II) phosphite, indicating Fe²⁺.
2. N₃S₇ – Trinitrogen heptasulfide:
This is a covalent compound made of nonmetals, so we use prefixes to indicate the number of atoms. “Tri-” for three nitrogen atoms and “hepta-” for seven sulfur atoms gives us Trinitrogen heptasulfide.
3. NH₃ – Ammonia:
NH₃ is a well-known covalent compound with a common name: ammonia. Though it could be named “nitrogen trihydride,” the common name is more widely accepted and used in practice.
4. H₂SeO₄ (aq) – Selenic acid:
This is an oxoacid (acid containing oxygen). The anion here is selenate (SeO₄²⁻). According to naming rules, “-ate” anions become “-ic acid” when naming acids. Therefore, H₂SeO₄ is selenic acid.
5. MnSO₄ · 6H₂O – Manganese(II) sulfate hexahydrate:
This is a hydrated ionic compound. Mn forms +2 ions here (sulfate is SO₄²⁻), so we name it Manganese(II) sulfate. The “· 6H₂O” indicates six water molecules per formula unit, which we denote as hexahydrate. Hence, the full name is Manganese(II) sulfate hexahydrate.
These naming conventions are based on IUPAC (International Union of Pure and Applied Chemistry) standards for chemical nomenclature.
