Question

Number of Cl=O bonds in chlorous acid, chloric acid and perchloric acid respectively are :

• A. 1, 1 and 3
• B. 3, 1 and 1
• C. 1, 2 and 3
• D. 4, 1 and 0

Hint:

To draw the structures of oxyacids, remember that the acidic hydrogen is attached to an oxygen atom (forming a hydroxyl group). The remaining oxygen atoms are typically double-bonded to the central non-metal atom.

Answer 1

The Correct Option is C

Let's determine the structure and count the number of double bonds between chlorine and oxygen for each acid. The hydrogen atom is always bonded to an oxygen atom.
1. Chlorous acid (HClO$_2$): The central atom is chlorine (Cl). It is bonded to one hydroxyl group (-OH) and one oxygen atom. To satisfy the valency, the oxygen atom is double-bonded to chlorine. The structure is H-O-Cl=O.
Number of Cl=O bonds = 1.
2. Chloric acid (HClO$_3$): The central atom is Cl. It is bonded to one -OH group and two oxygen atoms. The two oxygen atoms are double-bonded to chlorine. The structure is H-O-Cl(=O)$_2$.
Number of Cl=O bonds = 2.
3. Perchloric acid (HClO$_4$): The central atom is Cl. It is bonded to one -OH group and three oxygen atoms. The three oxygen atoms are double-bonded to chlorine. The structure is H-O-Cl(=O)$_3$.
Number of Cl=O bonds = 3.
The respective numbers of Cl=O bonds are 1, 2, and 3.