Problem 15 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

Which of the following statements about \(\mathrm{Na}_{2} \mathrm{O}_{2}\) is not correct? (a) It is diamagnetic in nature (b) It is derivative of \(\mathrm{H}_{2} \mathrm{O}_{2}\) (c) \(\mathrm{Na}_{2} \mathrm{O}_{2}\) oxidises \(\mathrm{Cr}^{3+}\) to \(\mathrm{CrO}_{4}^{2-}\) in acid medium. (d) It is the super oxide of sodium

Step-by-Step Solution

Answer

Statement (d) is not correct.

Step 1: Analyzing Statement (a)

Sodium peroxide, \(\mathrm{Na}_{2} \mathrm{O}_{2}\), is made of sodium (\(\mathrm{Na^+}\)) and peroxide ions (\(\mathrm{O}_2^{2-}\)). The peroxide ion has all its electrons paired, making it a diamagnetic molecule. Hence, statement (a) is correct.

Step 2: Analyzing Statement (b)

\(\mathrm{Na}_{2} \mathrm{O}_{2}\) is sodium peroxide, which is a derivative of hydrogen peroxide \(\mathrm{H}_{2} \mathrm{O}_{2}\) because it contains the peroxide ion (\(\mathrm{O}_2^{2-}\)). Thus, statement (b) is correct.

Step 3: Analyzing Statement (c)

In acidic medium, \(\mathrm{Na}_{2} \mathrm{O}_{2}\) can act as an oxidizing agent, turning \(\mathrm{Cr}^{3+} \) ions into \(\mathrm{CrO}_{4}^{2-}\) ions. Therefore, statement (c) is correct.

Step 4: Analyzing Statement (d)

\(\mathrm{Na}_{2} \mathrm{O}_{2}\) is not a superoxide, but rather a peroxide. Superoxides contain the \(\mathrm{O}_2^{-}\) ion. Sodium superoxide is \(\mathrm{NaO}_2\). Thus, statement (d) is not correct.

Key Concepts

Diamagnetic Nature

In chemistry, the term 'diamagnetic' refers to substances where all electrons are paired. These substances do not have any unpaired electrons and are generally weakly repelled by magnetic fields. Sodium peroxide, or \(\mathrm{Na}_{2} \mathrm{O}_{2}\), exhibits diamagnetic properties due to the nature of its peroxide ion \((\mathrm{O}_2^{2-})\).
The peroxide ion serves as the key component here because it has a total of 18 electrons, specifically 8 from each oxygen atom plus 2 additional electrons. These electrons are paired into molecular orbitals, resulting in a diamagnetic molecule.
Understanding diamagnetism is important in analyzing the magnetic behavior of different compounds, particularly in distinguishing between the diverse interactions substances have with magnetic fields. This property directly affects how materials behave when subject to external magnetic fields.

Peroxide Derivatives

Peroxide derivatives are compounds containing the peroxide ion \(\mathrm{O}_2^{2-}\). They are known for their characteristic oxygen-oxygen single bond. Sodium peroxide \(\mathrm{Na}_{2} \mathrm{O}_{2}\), stands as a classic example of such a derivative.
The close relationship between sodium peroxide and hydrogen peroxide \(\mathrm{H}_{2} \mathrm{O}_{2}\) arises from their shared peroxide ion. This structural similarity is fundamental, as both compounds involve the potent oxidizing unit of \(\mathrm{O}_2^{2-}\).

• Hydrogen peroxide itself is a simple peroxide, consisting of two hydrogen atoms bonded to a peroxide ion.
• Sodium peroxide, on the other hand, replaces hydrogen with two sodium ions, each balancing the charge of the peroxide ion.

Understanding these derivatives helps to advance the broader field of chemical reactivity and stability studies. In particular, these insights clarify how similar derivatives function or how they can be transformed chemically for various applications.

Oxidizing Agents

Oxidizing agents are substances that gain electrons in a chemical reaction, thereby causing another substance to lose electrons, which is termed as oxidizing that substance. In the realm of redox reactions, sodium peroxide \(\mathrm{Na}_{2} \mathrm{O}_{2}\) adeptly fulfills this role.
When dissolved in acidic media, sodium peroxide demonstrates its oxidative nature by facilitating the transformation of \(\mathrm{Cr}^{3+}\) ions into \(\mathrm{CrO}_{4}^{2-}\) ions. Let's break down how this happens:

• The peroxide ion \((\mathrm{O}_2^{2-})\) can donate oxygen, leading to the oxidation of \(\mathrm{Cr}^{3+}\).
• This reaction underscores sodium peroxide's potential as an oxidizing agent, releasing oxygen which reacts further with electron-rich substances.

Reactions involving oxidizing agents are pivotal in numerous scientific and industrial processes, ranging from simple laboratory oxidations to large-scale environmental applications. Sodium peroxide's robust ability to oxidize makes it a valuable subject of study in fields like environmental chemistry and materials manufacturing.