For the following oxo acids, choose the increasing order of their  acidity:

A. \(HClO < HClO_2 < HClO_4 < HClO_3\)

B. \(HClO_4 < HClO_2 < HClO_3 < HClO\)

C. \(HClO_3 < HClO_4 < HClO_2 < HClO\)

D. \(HClO < HClO_2 < HClO_3 < HClO_4\)

Choose the correct answer from the options given below:

D

The correct answer is option 2. D.

To understand the increasing order of acidity for the oxo acids of chlorine, let us break down the factors influencing their acidity and analyze each acid in detail.

Factors Influencing Acidity

Number of Oxygen Atoms:  In oxo acids (acids where oxygen is bound to the central atom), the acidity increases with the number of oxygen atoms. This is because more oxygen atoms help to stabilize the negative charge on the conjugate base through inductive effects and resonance.

Oxidation State of the Central Atom: The oxidation state of the central atom also affects acidity. A higher oxidation state increases the positive character of the central atom, making it easier to stabilize the negative charge on the conjugate base.

Analysis of Each Acid

Hypochlorous Acid (\(HClO\)):

The conjugate base is \(ClO^-\). The single oxygen atom provides limited stabilization of the negative charge. Therefore, \(HClO\) is the least acidic among the oxo acids of chlorine.

Chlorous Acid (\(HClO_2\)):

The conjugate base is \(ClO_2^-\). The additional oxygen atom provides more stabilization through inductive effects and resonance compared to \(HClO\). Thus, \(HClO_2\) is more acidic than \(HClO\).

Chloric Acid (\(HClO_3\)):

The conjugate base is \(ClO_3^-\). With three oxygen atoms, this acid is more acidic than both \(HClO\) and \(HClO_2\), due to even greater stabilization of the negative charge.

Perchloric Acid (\(HClO_4\)):

The conjugate base is \(ClO_4^-\). The highest number of oxygen atoms in this acid provides the maximum stabilization of the negative charge through extensive resonance and inductive effects. Consequently, \(HClO_4\) is the most acidic among the oxo acids of chlorine.

Summary of Acidity Order

Hypochlorous Acid (\(HClO\)): Least acidic, with only one oxygen atom for stabilization.

Chlorous Acid (\(HClO_2\)): More acidic than \(HClO\), with two oxygen atoms for stabilization.

Chloric Acid (\(HClO_3\)): More acidic than \(HClO_2\), with three oxygen atoms for stabilization.

Perchloric Acid (\(HClO_4\)): Most acidic, with four oxygen atoms for stabilization.

Therefore, the increasing order of acidity is: \(HClO < HClO_2 < HClO_3 < HClO_4\)

The correct answer is option 2: D.