Problem 4 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

Which of the following liberates \(\mathrm{O}_{2}\) upon hydrolysis? (a) \(\mathrm{Pb}_{3} \mathrm{O}_{4}\) (b) \(\mathrm{KO}_{2}\) (c) \(\mathrm{Na}_{2} \mathrm{O}_{2}\) (d) \(\mathrm{Li}_{2} \mathrm{O}_{2}\)

Step-by-Step Solution

Answer

(b) \( \mathrm{KO}_{2} \), (c) \( \mathrm{Na}_{2} \mathrm{O}_{2} \), and (d) \( \mathrm{Li}_{2} \mathrm{O}_{2} \) liberate \( \mathrm{O}_{2} \) upon hydrolysis.

Step 1: Understanding Hydrolysis

Hydrolysis is the reaction of a compound with water. We need to determine which compound, when reacted with water, will produce oxygen gas, \( \mathrm{O}_2 \).

Step 2: Examining Each Compound

Let's examine each compound:(a) \( \mathrm{Pb}_3\mathrm{O}_4 \) is a mixed oxide, often called red lead. When it reacts with water, it doesn't produce \( \mathrm{O}_2 \).(b) \( \mathrm{KO}_2 \) is potassium superoxide. Superoxides release oxygen gas upon reacting with water.(c) \( \mathrm{Na}_2\mathrm{O}_2 \) is sodium peroxide, which also produces \( \mathrm{O}_2 \) when it reacts with water.(d) \( \mathrm{Li}_2\mathrm{O}_2 \) is lithium peroxide. Like sodium peroxide, it can liberate \( \mathrm{O}_2 \) when hydrolyzed.

Step 3: Reaction of \( \mathrm{KO}_2 \) with Water

The reaction of \( \mathrm{KO}_2 \) with water is:\[ 4\, \mathrm{KO}_2 + 2\, \mathrm{H}_2\mathrm{O} \rightarrow 4\, \mathrm{KOH} + 3\, \mathrm{O}_2 \]This reaction clearly produces \( \mathrm{O}_2 \).

Step 4: Reaction of \( \mathrm{Na}_2 \mathrm{O}_2 \) with Water

The reaction of \( \mathrm{Na}_2 \mathrm{O}_2 \) with water is:\[ 2\, \mathrm{Na}_2\mathrm{O}_2 + 2\, \mathrm{H}_2\mathrm{O} \rightarrow 4\, \mathrm{NaOH} + \mathrm{O}_2 \]This also liberates \( \mathrm{O}_2 \).

Step 5: Reaction of \( \mathrm{Li}_2 \mathrm{O}_2 \) with Water

The reaction of \( \mathrm{Li}_2 \mathrm{O}_2 \) with water is:\[ 2\, \mathrm{Li}_2\mathrm{O}_2 + 2\, \mathrm{H}_2\mathrm{O} \rightarrow 4\, \mathrm{LiOH} + \mathrm{O}_2 \]Again, this reaction produces \( \mathrm{O}_2 \).

Step 6: Concluding Which Compounds Liberate \( \mathrm{O}_{2} \)

From the reactions, options (b), (c), and (d) release \( \mathrm{O}_2 \) when they undergo hydrolysis. Option (a) does not produce \( \mathrm{O}_2 \) when reacted with water.

Key Concepts

Potassium Superoxide Reaction

When potassium superoxide (\( \mathrm{KO}_2 \)) reacts with water, it undergoes a fascinating chemical transformation. Potassium superoxide is known for its ability to liberate oxygen gas, \( \mathrm{O}_2 \), when it reacts with water.
The chemical equation for this reaction is:
\[4\, \mathrm{KO}_2 + 2\, \mathrm{H}_2\mathrm{O} \rightarrow 4\, \mathrm{KOH} + 3\, \mathrm{O}_2\]
This equation shows that four molecules of \( \mathrm{KO}_2 \) react with two molecules of water to form four molecules of potassium hydroxide (\( \mathrm{KOH} \)) and three molecules of oxygen gas.
The production of \( \mathrm{O}_2 \) makes \( \mathrm{KO}_2 \) particularly interesting for applications where a reliable source of oxygen is needed, such as in spacesuits and submarines.

• It's important to note that \( \mathrm{KO}_2 \) is sensitive to moisture and should be handled with care.
• This ability to release \( \mathrm{O}_2 \) also makes it useful in regeneration systems, refreshing environments with breathable air.

Sodium Peroxide Reaction

Sodium peroxide (\( \mathrm{Na}_2\mathrm{O}_2 \)), like potassium superoxide, reacts with water to release oxygen gas. This reaction highlights sodium peroxide's role as an oxidizing agent.
The equation for this reaction is given by:
\[2\, \mathrm{Na}_2\mathrm{O}_2 + 2\, \mathrm{H}_2\mathrm{O} \rightarrow 4\, \mathrm{NaOH} + \mathrm{O}_2\]
Here, two molecules of \( \mathrm{Na}_2\mathrm{O}_2 \) react with water, producing four molecules of sodium hydroxide (\( \mathrm{NaOH} \)) and a single molecule of oxygen.
The significance of \( \mathrm{Na}_2\mathrm{O}_2 \) in oxygen generation is notable in chemical oxygen generators that are used in environments needing purified and controlled air supply.

• \( \mathrm{Na}_2\mathrm{O}_2 \) can also serve as an efficient bleaching agent in various industrial applications due to its oxidative properties.
• Its ability to react and release \( \mathrm{O}_2 \) is beneficial in both emergency and sustained oxygen supply situations.

Lithium Peroxide Reaction

Lithium peroxide (\( \mathrm{Li}_2\mathrm{O}_2 \)) is another compound that releases oxygen when it reacts with water. This reaction illustrates its role as an oxygen generator.
The reaction can be described with the following equation:
\[2\, \mathrm{Li}_2\mathrm{O}_2 + 2\, \mathrm{H}_2\mathrm{O} \rightarrow 4\, \mathrm{LiOH} + \mathrm{O}_2\]
In this process, two molecules of \( \mathrm{Li}_2\mathrm{O}_2 \) combine with water to yield four molecules of lithium hydroxide (\( \mathrm{LiOH} \)) and oxygen.
Besides being useful in emergency oxygen systems, \( \mathrm{Li}_2\mathrm{O}_2 \) is of interest in rechargeable battery technologies, particularly in lithium-air batteries.

• These batteries leverage the release of oxygen to enhance the energy density, making them a promising technology for future energy storage solutions.
• This characteristic allows \( \mathrm{Li}_2\mathrm{O}_2 \) to play a dual role in both energy generation and oxygen supply systems.