Answer :
A compund is made up of iron and oxygen, only. The ratio of iron ions to oxide irons is 2:3 in this compund. The IUPAC name for this compound is Iron (III) Oxide.
Answer: The correct option is 3.
Explanation: We are given a compound which is made up of iron and oxygen only. The ratio of the two are given as:
[tex]\frac{\text{iron ions}}{\text{oxide ions}}=\frac{2}{3}[/tex]
This means that, number of iron ions are 2
Number of oxide ions are 3
From the above information, the formula becomes : [tex]Fe_2O_3[/tex]
The valency of iron = 3
Valency of oxide = 2
This compound is named as iron (III) oxide.
Hence, the correct option is 3
