Question

A compound ' \(\mathrm{x}\) ' is formed by slowly adding calculated quantities of sodium peroxide to ice cold \(20 \%\) solution of the sulphuric acid. Which of the following incorrectly describes the compound ' \(x\) '? (1) It is a mild bleaching agent and its bleaching action is due to reduction. (2) When shaken with potassium dichromate in sulphuric acid and ether, a blue colour is obtained in the ether layer. (3) It is a strong oxidizing agent in acidic medium and has no oxidizing power in alkaline medium. (4) It is a weak monobasic acid. (a) \(2,3,4\) (b) \(1,3,4\) (c) 1,2 , (d) \(1,2,3\)

Short answer

The correct answer is (b) 1, 3, 4.

Step-by-step solution

Identify the Compound

The reaction between sodium peroxide and sulfuric acid produces hydrogen peroxide (\( \text{H}_2\text{O}_2 \)). This compound is known for its oxidizing and bleaching properties.

Evaluate Statement 1

Statement 1 claims that \( \text{H}_2\text{O}_2 \) is a mild bleaching agent due to reduction. However, \( \text{H}_2\text{O}_2 \) bleaches through oxidation, not reduction, as it releases oxygen which oxidizes the stain. Thus, Statement 1 is incorrect.

Evaluate Statement 2

When hydrogen peroxide is shaken with potassium dichromate in sulfuric acid and ether, a blue color indeed forms in the ether layer due to the formation of perchromic acid. Therefore, Statement 2 is correct.

Evaluate Statement 3

Hydrogen peroxide is indeed a strong oxidizing agent in acidic medium but it also retains oxidizing power in alkaline medium. Thus, Statement 3, which mentions no oxidizing power in an alkaline medium, is incorrect.

Evaluate Statement 4

Hydrogen peroxide is not an acid in the traditional sense but acts as a weak monobasic acid when dissolved in water. Thus, Statement 4 is incorrect in labeling \( \text{H}_2\text{O}_2 \) strictly as a weak monobasic acid without context.

Key concepts

Oxidizing Agent

Hydrogen peroxide ( H_2O_2) is a fascinating compound often highlighted for its role as an oxidizing agent. An oxidizing agent is a substance that has the ability to oxidize other substances, meaning it can accept electrons.

In chemical reactions, H_2O_2 plays a dual role, being capable of acting both as an oxidizing and a reducing agent depending on the substances it reacts with. It is, however, more prominently known for its oxidizing abilities, especially in acidic media.

When H_2O_2 oxidizes a substance, it can decompose to produce water and oxygen. The oxygen released in this process often reacts with the other components in the reaction: \[ 2 H_2O_2 \rightarrow 2 H_2O + O_2 \] This capability is why H_2O_2 is widely used in applications such as disinfection and in various chemical industries.

Bleaching Properties

One of the notable qualities of hydrogen peroxide is its bleaching property. This makes it a popular choice for whitening teeth and hair as well as in papermaking and textile industries to bleach paper and fabrics, respectively.

The effectiveness of H_2O_2 as a bleaching agent is due to its ability to break down and release oxygen radicals. These oxygen radicals are highly reactive and work by oxidizing the color compounds in stains: - Once applied to a stain, H_2O_2 releases oxygen atoms. - These atoms react with the colored compounds, leading to oxidation which changes their structure. - The altered structure appears lighter, thus achieving the bleaching effect.

Acidic and Alkaline Media

The behavior of hydrogen peroxide as an oxidizing agent can vary significantly based on the pH of the surrounding environment. - **Acidic Media:** In an acidic solution, H_2O_2 exhibits strong oxidizing properties. It can convert substances to their oxygenated forms more efficiently because the acidic conditions promote the stability and reactivity of H_2O_2. - **Alkaline Media:** In contrast, H_2O_2 still functions as an oxidizer in alkaline conditions, but its oxidizing power is reduced. The presence of hydroxide ions can lead to the decomposition of H_2O_2, reducing its effectiveness: \[ H_2O_2 + 2 OH^- \rightarrow 2 H_2O + O_2 \] Nonetheless, hydrogen peroxide remains versatile in various pH conditions, making it useful in numerous chemical applications.

Perchromic Acid Formation

One particularly intriguing reaction involving hydrogen peroxide is its interaction with potassium dichromate in sulfuric acid and ether, leading to perchromic acid formation.
When H_2O_2 comes in contact with potassium dichromate in the presence of sulfuric acid and ether, a reaction occurs that produces perchromic acid, which is characterized by its distinct blue color appearing in the ether layer: - The dichromate ion is reduced in the presence of hydrogen peroxide, while the H_2O_2 gets oxidized. - This redox reaction results in the formation of chromium species that are solvated in the ether, which gives rise to the blue-colored layer. This outcome exemplifies the strong oxidizing potential of H_2O_2 and its ability to engage in complex chemical transformations.