Give the name from the formula or the formula from the name for each of the following hydrated ionic compounds. Part A FeI2â‹…4H2O Spell out the full name of the compound. Part B nickel(II) nitrate heptahydrate Express your answer as a chemical formula. Part D beryllium sulfite tetrahydrate Express your answer as a chemical formula.
The Correct Answer and Explanation is:
Here are the correct answers for each part:
Part A: FeI₂·4H₂O
Name: Iron(II) iodide tetrahydrate
Explanation:
To name this compound, start with the ionic portion:
- Fe is the symbol for iron. Since iron is a transition metal that can have more than one possible charge, we need to determine its charge.
- The subscript 2 on I (iodide) shows there are two iodide ions (I⁻), each with a -1 charge, for a total of -2. Therefore, iron must have a +2 charge to balance the -2 from the iodide ions.
- Iron with a +2 charge is written as iron(II).
- Iodine forms the iodide ion (I⁻), so FeI₂ is named iron(II) iodide.
- The ·4H₂O indicates four water molecules are attached to each formula unit of the salt. This is written as tetrahydrate.
Thus, the full name is iron(II) iodide tetrahydrate.
Part B: Nickel(II) nitrate heptahydrate
Formula: Ni(NO₃)₂·7H₂O
Explanation:
- Nickel(II) means the nickel ion has a +2 charge (Ni²⁺).
- Nitrate is a polyatomic ion with the formula NO₃⁻ and a -1 charge.
- To balance the +2 from nickel, two nitrate ions are needed: (NO₃)₂.
- Heptahydrate means seven water molecules are attached.
So, the formula is Ni(NO₃)₂·7H₂O.
Part D: Beryllium sulfite tetrahydrate
Formula: BeSO₃·4H₂O
Explanation:
- Beryllium is a Group 2 metal with a +2 charge (Be²⁺).
- Sulfite is the polyatomic ion SO₃²⁻ with a -2 charge.
- One beryllium ion and one sulfite ion balance each other: BeSO₃.
- Tetrahydrate means four water molecules are included.
Therefore, the formula is BeSO₃·4H₂O.
In summary:
- Part A: Iron(II) iodide tetrahydrate
- Part B: Ni(NO₃)₂·7H₂O
- Part D: BeSO₃·4H₂O
Hydrated ionic compounds are named by combining the salt name with a Greek prefix indicating the number of water molecules.
