Question

What is the correct name for $Fe{(OH)_3}$?
(A) Iron (III) hydroxide
(B) Iron hydroxide (III)
(C) (III) iron hydroxide
(D) Iron (III) hydroxate
(E) Iron hydroxate (III)

Answer 1

The oxidation state of the metal is written between the name of the anion and the metal present in the compound. The name of the metal is written before the name of the anion in the nomenclature of inorganic compounds.

Complete step by step solution:
We will see how the name of certain inorganic compounds is given.
-We know that inorganic compounds involve cations or anions. If the molecule is covalent, then there will be partial positive and partial negative charges on the respective atoms.
-So, in order to give the name to an inorganic compound, we first write the name of the cation or metal. If we are using the name of the cation, then it will describe the oxidation state of the cation. But in case we are using the name of the metal itself, then we need to write the oxidation state of the metal at the right of the name of the metal.
-Then we write the name of the anions accordingly in order to give a complete name to the compound. Here, we do not need to show the number of anions present in the molecule because it can be predicted using the oxidation state of the metal and the charge on the anion.
-So, in the given compound, iron is in +3 oxidation state which is evident from the fact that there is no overall charge on the compound and hydroxyl ions have charge of (-1). When hydroxyl ions are as anions in the compounds, they are named as ‘hydroxide’.
So, the name of the compound given to us will be Iron (III) hydroxide. Here, (III) shows the oxidation state of iron.

Therefore, the correct answer to this question is (A).

Note: Do not get confused between hydroxide and hydroxate. In neutral inorganic compounds, $O{H^ - }$ ions are always named as hydroxide ions. Note that we can also write this compound’s name as Ferric hydroxide. Here, ferric shows the oxidation state of the iron, so we do not need to write (III) here.