Problem 115 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following statements about \(\mathrm{N}_{2} \mathrm{O}\) are correct? (1) \(\mathrm{NO}_{2}\) supports the combustion of phosphorous and sulphur (2) \(\mathrm{N}_{2} \mathrm{O}\) is a linear asymmetrical molecule, \(\mathrm{N}-\mathrm{N}-\mathrm{O}\).(3) \(\mathrm{N}_{2} \mathrm{O}\) is a bent molecule (a) 1,2 and 3 (b) 2 and 4 only (4) \(\mathrm{N}_{2} \mathrm{O}\) is reduced to \(\mathrm{N}_{2}\) when passed over hot copper (c) 1,2 and 4 (d) 2,3 and 4

Step-by-Step Solution

Answer

The correct statements are 4 only, so the answer is not provided in the given choices.

Step 1: Evaluate Statement 1

Statement 1 claims that \( \text{NO}_{2} \) supports the combustion of phosphorous and sulphur. This statement is incorrect for \( \text{NO}_{2} \), but it's worth noting that \( \text{N}_{2}\text{O} \) does support combustion. Therefore, Statement 1 is incorrect in the context of \( \text{NO}_{2} \).

Step 2: Evaluate Statement 2

Statement 2 claims that \( \text{N}_{2} \text{O} \) is a linear molecule with an asymmetrical structure \( \text{N}- \text{N}- \text{O} \). However, \( \text{N}_{2} \text{O} \) is indeed linear but symmetrical as a whole due to its structure and internal bond angles. Thus, Statement 2 is incorrect when considering symmetry.

Step 3: Evaluate Statement 3

Statement 3 claims that \( \text{N}_{2} \text{O} \) is a bent molecule. Given that \( \text{N}_{2} \text{O} \) is linear with a bond angle of 180 degrees, this statement is incorrect.

Step 4: Evaluate Statement 4

Statement 4 claims that \( \text{N}_{2} \text{O} \) is reduced to \( \text{N}_{2} \) when passed over hot copper. This is correct, as copper acts as a reducing agent turning \( \text{N}_{2} \text{O} \) into \( \text{N}_{2} \).

Key Concepts

Linear Molecules

Some molecules, like nitrous oxide (), are classified as linear molecules. This means that the atoms within the molecule are arranged in a straight line. In the case of , the molecule consists of two nitrogen atoms and one oxygen atom arranged as N-N-O. The key feature is the bond angle measuring 180 degrees, which ensures that all three atoms lie on the same axis.

Linear molecules can be symmetrical if the distribution of electrons across the molecule is even. This symmetry or asymmetry affects the molecule's polarity, influencing how it interacts with other molecules. In the case of , while it is linear, the differing electronegativities of nitrogen and oxygen could indicate asymmetry. However, the molecule's linear structure contributes to its overall spatial arrangement, often classified as symmetrical, containing evenly distributed electronic charges that neutralize each other.

Combustion Reaction

Combustion reactions are chemical processes where a substance reacts rapidly with oxygen to release energy. In many cases, this results in the production of heat and light, usually in the form of flames.  is notable for being capable of supporting combustion under certain conditions, which involves reacting with other substances, like phosphorous and sulfur, to sustain the fiery process.

When discussing these reactions, it's essential to consider both oxygenated species and reactants capable of sustaining an exothermic reaction. This ability to propagate combustion is crucial for understanding various industrial processes and even some natural biochemical cycles. For instance, nitrous oxide is often used as an oxidizer in rocket propellants and racing vehicles due to its potent oxidizing capacity, which can act analogously to oxygen in combustion.

Reduction with Copper

Reduction is a fundamental concept in chemistry, describing a chemical reaction in which a molecule gains electrons or decreases its oxidation state. The reduction of  when it interacts with copper is an important example.

In this process, hot copper acts as a reducing agent. When nitrogen monoxide passes over it, the copper donates electrons to the , thereby reducing it to nitrogen gas (). This is beneficial in removing nitrous compounds from emissions or atmospheric tests. Moreover, this property of copper and its efficiency as a reducing agent is utilized in various industrial settings for purifying gases or during specific chemical syntheses.

Understanding reduction, and particularly how different substances serve as reducing or oxidizing agents, helps in controlling and harnessing these reactions for desired outcomes, making it a crucial part of chemical education and practice.