What is the correct IUPAC-style name for Fe(OH)3?

What is the correct IUPAC-style name for Fe(OH)3?

• A. Iron hydroxide
• B. Iron (III) hydroxide
• C. Ferric hydroxide
• D. Iron oxide hydroxide

Answer: (B)

In naming compounds with metals that can have multiple oxidation states, we include the oxidation state of the metal in parentheses after the metal name. For Fe(OH)3, the three hydroxide (OH−) groups carry a total charge of −3. To balance that, iron must be in the +3 oxidation state. So the conventional IUPAC name is Iron (III) hydroxide, with the (III) indicating +3. Iron hydroxide omits the oxidation state and can be ambiguous about which iron oxidation state is present. Ferric hydroxide is a common name but not the IUPAC form. Iron oxide hydroxide would imply the presence of oxide (O2−) as well, which is not the case here since the compound consists of Fe(III) and hydroxide ligands only.

In naming compounds with metals that can have multiple oxidation states, we include the oxidation state of the metal in parentheses after the metal name. For Fe(OH)3, the three hydroxide (OH−) groups carry a total charge of −3. To balance that, iron must be in the +3 oxidation state. So the conventional IUPAC name is Iron (III) hydroxide, with the (III) indicating +3.

Iron hydroxide omits the oxidation state and can be ambiguous about which iron oxidation state is present. Ferric hydroxide is a common name but not the IUPAC form. Iron oxide hydroxide would imply the presence of oxide (O2−) as well, which is not the case here since the compound consists of Fe(III) and hydroxide ligands only.