Question

fei₂·4h₂o
spell out the full name of the compound.

part b
nickel(ii) nitrate heptahydrate
express your answer as a chemical formula.

Explanation:

Part A

Step1: Identify the cation and anion

The compound is \( \text{FeI}_2 \cdot 4\text{H}_2\text{O} \). The cation is \( \text{Fe}^{2+} \) (since \( \text{I}^- \) has a charge of -1 and there are 2 \( \text{I}^- \) ions, so Fe must be +2 to balance the charge), named iron(II). The anion is iodide (\( \text{I}^- \)). The water molecules are hydrates, with 4 water molecules, so "tetrahydrate".

Step2: Combine the names

Combine the name of the ionic compound and the hydrate. The ionic compound is iron(II) iodide, and with 4 water molecules, it's iron(II) iodide tetrahydrate.

Step1: Identify the ions and hydrate

Nickel(II) means \( \text{Ni}^{2+} \), nitrate is \( \text{NO}_3^- \). The formula for nickel(II) nitrate is \( \text{Ni(NO}_3\text{)}_2 \) (since \( \text{Ni}^{2+} \) and \( \text{NO}_3^- \) (charge -1) require 2 nitrates to balance). Heptahydrate means 7 water molecules (\( \text{H}_2\text{O} \)).

Step2: Write the formula

Combine the nickel(II) nitrate and the 7 water molecules. So the formula is \( \text{Ni(NO}_3\text{)}_2 \cdot 7\text{H}_2\text{O} \).

Answer:

iron(II) iodide tetrahydrate

Part B