Problem 46 - A Complete Resource Book in Chemistry for JEE Main

Question

Oxygen does not react with (a) \(\mathrm{Na}\) (b) \(\mathrm{P}\) (c) \(\mathrm{Cl}\) (d) \(\mathrm{S}\)

Step-by-Step Solution

Answer

Chlorine (Cl) does not react with oxygen to form stable oxides.

Step 1: Understand the Problem

We are asked to identify which of the given elements (sodium \( \mathrm{Na} \), phosphorus \( \mathrm{P} \), chlorine \( \mathrm{Cl} \), or sulfur \( \mathrm{S} \)) does not react with oxygen. Let's start by understanding the reactivity of these elements with oxygen.

Step 2: Analyze Sodium (Na) Reaction with Oxygen

Sodium (\( \mathrm{Na} \)) is an alkali metal and reacts readily with oxygen to form sodium oxide (\( \mathrm{Na}_2\mathrm{O} \)).

Step 3: Analyze Phosphorus (P) Reaction with Oxygen

Phosphorus (\( \mathrm{P} \)) is a non-metal that reacts readily with oxygen to form phosphorus pentoxide (\( \mathrm{P}_4\mathrm{O}_{10} \)).

Step 4: Analyze Chlorine (Cl) Reaction with Oxygen

Chlorine (\( \mathrm{Cl} \)) is a halogen and is generally not known to react directly with oxygen under normal conditions to form stable oxides.

Step 5: Analyze Sulfur (S) Reaction with Oxygen

Sulfur (\( \mathrm{S} \)) is a non-metal that reacts with oxygen to form sulfur dioxide (\( \mathrm{SO}_2 \)) and can further oxidize to \( \mathrm{SO}_3 \).

Step 6: Conclusion on Which Element Does Not React with Oxygen

Based on the analysis, chlorine (\( \mathrm{Cl} \)) is the element that does not react with oxygen to form stable oxides under normal conditions.

Key Concepts

Sodium and Oxygen Reaction

Sodium, represented by the symbol \( \mathrm{Na} \), is classified as an alkali metal. Alkali metals are known for their high reactivity, especially with oxygen and water. When sodium comes into contact with oxygen, it undergoes a chemical reaction to form sodium oxide. The reaction is as follows: \[ 4\mathrm{Na} + \mathrm{O}_2 \rightarrow 2\mathrm{Na}_2\mathrm{O} \] This exothermic reaction is quite vigorous, releasing a fair amount of heat. The sodium oxide produced here appears as a white powder. This characteristic reactivity with oxygen classifies sodium as a highly reactive element, interacting swiftly with atmospheric oxygen to produce such compounds. For safety, sodium is often stored under mineral oil or in an inert environment to prevent unintended reactions.

Phosphorus and Oxygen Reaction

Phosphorus, denoted as \( \mathrm{P} \), is a fascinating non-metal that exhibits vigorous reactivity with oxygen. When phosphorus is exposed to oxygen, it tends to ignite spontaneously in air to produce phosphorus pentoxide, a common oxide of phosphorus. The chemical equation governing this reaction is: \[ 4\mathrm{P} + 5\mathrm{O}_2 \rightarrow 2\mathrm{P}_4\mathrm{O}_{10} \] Phosphorus pentoxide is a white, crystalline solid that forms acid anhydrides when dissolved in water, leading to the formation of phosphoric acid. The reactivity is so pronounced that phosphorus must be handled with caution and is often stored under water to avoid accidental combustion. Its willingness to react with oxygen showcases the highly reactive nature of phosphorus as a non-metal.

Chlorine Stability

Chlorine, symbolized as \( \mathrm{Cl} \), belongs to the group of halogens. Unlike sodium and phosphorus, chlorine does not easily react with oxygen under normal conditions. It is quite stable due to its electronic configuration, which generally does not favor forming stable oxides with oxygen. This lack of reactivity is attributable to the fact that chlorine atoms prefer gaining a single electron to achieve a stable electron configuration rather than forming compounds with oxygen atoms. Furthermore, in direct atmospheric conditions, chlorine remains as a diatomic molecule \( \mathrm{Cl}_2 \) and does not readily form stable compounds like oxides. This stability can be beneficial, making chlorine useful in different applications where reactive halogens could pose risks. Its non-reactivity with oxygen is a notable exception among the elements being discussed.

Sulfur and Oxygen Reaction

Sulfur, termed \( \mathrm{S} \), is another non-metal known for its active reaction with oxygen. When sulfur comes in contact with oxygen, it typically forms sulfur dioxide (\( \mathrm{SO}_2 \)), which can further oxidize to produce sulfur trioxide (\( \mathrm{SO}_3 \)). The initial reaction shows sulfur's affinity for oxidation: \[ \mathrm{S} + \mathrm{O}_2 \rightarrow \mathrm{SO}_2 \] Upon further oxidation, it can form: \[ 2\mathrm{SO}_2 + \mathrm{O}_2 \rightarrow 2\mathrm{SO}_3 \] These reactions are fundamental in forming substances like sulfuric acid in nature. Sulfur dioxide is a colorless gas with a distinct, pungent smell, while sulfur trioxide is a component of acid rains. Because of its reactive nature, sulfur finds numerous industrial applications, yet it needs to be handled carefully to mitigate environmental impacts.