Question

iron(iii) hydroxide is present in rust. which of the following gives the correct formula and bonding for iron(iii) hydroxide?
○ fe(oh)₃; covalent
○ fe₃oh; ionic
○ fe(oh)₃; ionic
○ fe₃oh; covalent

Explanation:

Step1: Determine the formula

Iron(III) has a charge of \( +3 \) (\( \text{Fe}^{3+} \)), and hydroxide ion is \( \text{OH}^- \) (charge \( -1 \)). To balance charges, we need 3 \( \text{OH}^- \) for 1 \( \text{Fe}^{3+} \), so the formula is \( \text{Fe(OH)}_3 \).

Step2: Determine the bonding type

Iron(III) hydroxide is a compound formed between a metal ion (\( \text{Fe}^{3+} \)) and polyatomic ions (\( \text{OH}^- \)). Compounds between metal ions and ions (including polyatomic ions) are ionic compounds, so the bonding is ionic.

Answer:

\( \text{Fe(OH)}_3 \); ionic (the option with formula \( \text{Fe(OH)}_3 \) and bonding ionic)