Problem 20 - A Complete Resource Book in Chemistry for JEE Main

Question

Which one of the following compounds undergo hydrolysis during distillation to yield hydrogen peroxide? (a) \(\mathrm{HNO}_{3}\) (b) \(\mathrm{H}_{4} \mathrm{P}_{2} \mathrm{O}_{7}\) (c) \(\mathrm{H}_{2} \mathrm{~S}_{2} \mathrm{O}_{8}\) (d) \(\mathrm{H}_{2} \mathrm{~S}_{2} \mathrm{O}_{6}\)

Step-by-Step Solution

Answer

The compound \\(\text{H}_2\text{S}_2\text{O}_8\\) (peroxydisulfuric acid) undergoes hydrolysis to yield hydrogen peroxide.

Step 1: Understanding Hydrolysis

Hydrolysis refers to a reaction where a compound reacts with water, often resulting in the breakdown of that compound into multiple products. For our question, we need a compound that hydrolyzes to produce hydrogen peroxide, \(\text{H}_2\text{O}_2\).

Step 2: Examine Each Option

- \(\text{HNO}_3\): Nitric acid does not produce hydrogen peroxide upon hydrolysis.- \(\text{H}_4\text{P}_2\text{O}_7\): Pyrophosphoric acid breaks down into simpler phosphoric acid units but does not yield hydrogen peroxide.- \(\text{H}_2\text{S}_2\text{O}_8\): Peroxydisulfuric acid can undergo hydrolysis to give hydrogen peroxide and other sulfur-oxygen acids.- \(\text{H}_2\text{S}_2\text{O}_6\): Thiosulfuric acid itself undergoes decomposition and does not yield hydrogen peroxide.

Step 3: Analyzing Option (c)

The hydrolysis of \(\text{H}_2\text{S}_2\text{O}_8\) (peroxydisulfuric acid) can be represented as: \[\text{H}_2\text{S}_2\text{O}_8 + 2\ \text{H}_2\text{O} \longrightarrow \text{H}_2\text{O}_2 + 2 \ \text{H}_2\text{SO}_4\]This reaction clearly shows the formation of hydrogen peroxide as a byproduct, indicating this compound undergoes hydrolysis to yield hydrogen peroxide.

Step 4: Conclusion

Based on the hydrolysis reactions analyzed, only \(\text{H}_2\text{S}_2\text{O}_8\) undergoes hydrolysis to yield \(\text{H}_2\text{O}_2\). This compound is known to break down in water to form hydrogen peroxide.

Key Concepts

Hydrogen Peroxide Formation

Hydrogen peroxide is a simple compound with the chemical formula \( \text{H}_2\text{O}_2 \). It is well known for its disinfectant properties and use in bleaching. The interesting part about hydrogen peroxide is its formation through hydrolysis. Hydrolysis is a chemical process where water is used to break down compounds. In certain cases, compounds undergo hydrolysis to produce hydrogen peroxide as one of the products.

When we talk specifically about hydrogen peroxide formation through hydrolysis, we are often concerned with compounds known as peroxides. These compounds tend to have an extra oxygen-oxygen single bond that can readily form hydrogen peroxide when combined with water. Not all compounds can undergo hydrolysis to yield hydrogen peroxide; a compound must have the right chemical structure that includes this potential \( \text{-O-O-} \) linkage or a similar reactive group.

Peroxydisulfuric acid is one such compound that, when hydrolyzed, breaks down to form hydrogen peroxide and other sulfur-containing acids. Understanding how this transformation occurs helps in grasping the broader concept of controlled chemical reactions yielding specific desired products, such as hydrogen peroxide.

Peroxydisulfuric Acid

Peroxydisulfuric acid is a strong oxidizing agent with the formula \( \text{H}_2\text{S}_2\text{O}_8 \). It contains a unique peroxide linkage between two sulfur atoms \(( \text{-O-O-} )\). This structural component is what enables it to participate in hydrolysis, leading to the formation of hydrogen peroxide.

The presence of the peroxo linkage is the key here. When peroxydisulfuric acid reacts with water, this \( \text{-O-O-} \) group is subjected to cleavage. As a result, one of the products formed is hydrogen peroxide, \( \text{H}_2\text{O}_2 \), along with the generation of sulfuric acid, \( \text{H}_2\text{SO}_4 \).

In industrial and laboratory settings, this property makes peroxydisulfuric acid a valuable reactant in scenarios where hydrogen peroxide is desired. Understanding the behavior of peroxydisulfuric acid during hydrolysis not only explains its practical applications but also provides insights into reaction planning and chemical synthesis.

Chemical Reaction Analysis

Analyzing chemical reactions involves understanding the reactants and products involved as well as the mechanisms by which these reactions occur. In the context of hydrolysis reactions like that of peroxydisulfuric acid, this entails recognizing the breaking and forming of bonds driven by interactions with water molecules.

When analyzing hydrolysis, one should look for the presence of potential reactive groups in the compound. Identify bonds that can take part in breaking and reforming in the presence of water. Peroxydisulfuric acid's \( \text{-O-O-} \) bond is an example of such a reactive bond.

Furthermore, chemical reaction analysis includes stoichiometric calculations. Knowing that one molecule of \( \text{H}_2\text{S}_2\text{O}_8 \) reacts with two molecules of water to produce one molecule of hydrogen peroxide and two molecules of sulfuric acid helps verify the reaction's balance and predict product creation. This type of analysis ensures that the reactions are understood at a fundamental level, which is crucial in chemical research and industrial applications.