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 (4) \(\mathrm{N}_{2} \mathrm{O}\) is reduced to \(\mathrm{N}_{2}\) when passed over hot copper

Step-by-Step Solution

Answer

Statements (2) and (4) about \( \mathrm{N}_2 \mathrm{O} \) are correct.

Step 1: Analyze Statement (1)

Statement (1) claims that \( \mathrm{NO}_2 \) supports the combustion of phosphorous and sulphur. \( \mathrm{NO}_2 \), or nitrogen dioxide, is indeed capable of supporting combustion due to its oxygen content. Therefore, statement (1) is correct but note this is unrelated to \( \mathrm{N}_2 \mathrm{O} \), the molecule in question.

Step 2: Examine Statement (2)

Statement (2) describes \( \mathrm{N}_2 \mathrm{O} \) as a linear asymmetrical molecule with a \( \mathrm{N}-\mathrm{N}-\mathrm{O} \) configuration. \( \mathrm{N}_2 \mathrm{O} \), or nitrous oxide, in fact has a linear structure. The arrangement of atoms, nitrogen and oxygen, as linear makes this statement correct.

Step 3: Assess Statement (3)

Statement (3) claims \( \mathrm{N}_2 \mathrm{O} \) is a bent molecule. However, \( \mathrm{N}_2 \mathrm{O} \) has a linear geometry due to its molecular bonding and structure. Hence, statement (3) is incorrect.

Step 4: Validate Statement (4)

Statement (4) suggests that \( \mathrm{N}_2 \mathrm{O} \) is reduced to \( \mathrm{N}_2 \) when passed over hot copper. When \( \mathrm{N}_2 \mathrm{O} \) contacts hot copper, it can indeed be reduced to nitrogen gas \( \mathrm{N}_2 \), making this statement correct.

Key Concepts

Nitrous Oxide

Nitrous oxide, often known by its chemical formula \( \mathrm{N}_2\mathrm{O} \), is a simple and fascinating molecule. It is commonly referred to as "laughing gas" due to its euphoric effects when inhaled. This molecule consists of two nitrogen atoms and one oxygen atom, arranged in a linear structure. In chemistry, it is valued not only for its anesthetic qualities but also for its participation in a variety of reactions. Nitrous oxide acts as an oxidizer and finds use in a variety of applications, including the enhancement of engine performance by increasing the amount of available oxygen for combustion. Its linear configuration plays a vital role in its reaction properties and physical behavior.

Combustion Support

Combustion is a chemical process where a material reacts with oxygen, producing heat and light. Some molecules, like nitrogen dioxide \( \mathrm{NO}_2 \), contain oxygen and can support combustion. In contrast, nitrous oxide \( \mathrm{N}_2\mathrm{O} \), while capable of releasing oxygen under certain conditions, is generally used to enhance combustion indirectly. In practice, this means that when \( \mathrm{N}_2\mathrm{O} \) decomposes, it can produce oxygen that supports the burning of other substances. This property makes it useful in various applications from racing engines where it releases extra oxygen to burn more fuel, to rocket propellants in specific applications.

Reduction Reactions

Reduction is a fundamental chemical reaction where a molecule gains electrons. For nitrous oxide, when it passes over a hot metal surface like copper, a reduction reaction occurs. Specifically, nitrous oxide is reduced to nitrogen gas \( \mathrm{N}_2 \). This process involves the transfer of electrons and the change of oxidation states, transforming the nitrous oxide molecule into a more stable nitrogen gas. Understanding reduction reactions like these is essential in chemical engineering and environmental science, where such processes can be harnessed for energy production, pollution control, and chemical synthesis.

Linear Molecules

Linear molecules are characterized by the arrangement of their atoms along a straight line. In the case of nitrous oxide \( \mathrm{N}_2\mathrm{O} \), the molecule is linear because the central nitrogen atom forms 180-degree bond angles with the adjacent nitrogen and oxygen atoms. This geometry is the result of electron pair repulsion, which is minimized in a linear configuration. Linear molecular geometry affects the physical and chemical properties of a molecule, including how it interacts with other molecules and its energy states. Understanding these configurations helps predict molecular behavior in reactions and biological systems.