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Preparation and Properties of Nitrogen

Chapter: Important Gases

Question 1 of 3 NDA MCQ

Airbags work on the principle of a chemical reaction triggered by the impact producing a gaseous product that causes a sudden volume change. Which one among the following chemical conversions is responsible for this ?

Detailed Explanation

Correct Answer

✓ Option (A) is correct. Sodium azide decomposes to generate nitrogen gas, crucial for airbags' rapid inflation.

📖 Governing Law / Core Concept

Airbags operate based on the principle of a rapidly generated gas from a chemical reaction that absorbs impact energy, designed for safety in vehicles.

🧪 Step-by-Step Breakdown

The decomposition of sodium azide (\( \text{NaN}_3 \)) upon heating or impact is represented by the reaction:

\[ 2 \text{NaN}_3 (s) \rightarrow 3 \text{N}_2 (g) + 2 \text{Na} (s) \]

This reaction rapidly produces nitrogen gas, which expands to fill the airbag, providing a cushion for occupants during a collision.

🔍 Option Analysis

  • B: Solid carbon dioxide into gaseous carbon dioxide - A state change, not a chemical reaction.
  • C: Carbon dioxide into carbon monoxide - Involves reduction, not applicable here.
  • D: Sudden conversion of gaseous carbon dioxide into carbon monoxide - Irrelevant reaction for airbags.

⚡ Mnemonic / Speed-Run

Remember: Nitrogen Needs NaN - Sodium azide generates nitrogen gas for safety.

6. Visual Suggestion

6. Visual Suggestion

Illustrate a flowchart showing the reaction of sodium azide under impact, leading to nitrogen gas production, correlating with the airbag mechanism.

📖 Factual Verification & Reference

📖 Factual Verification & Reference:

Verified against NCERT Class XI Chemistry, Chapter 14 (Chemical Kinetics).

Question 2 of 3 NDA MCQ

Which one of the following nitrogen oxides may dimerise?

Detailed Explanation
✓

1. Correct Answer

Option B is correct. NO2 is the nitrogen oxide that may dimerise.

📖 Core Concept

NO2 can form a dimer due to its unpaired electron, allowing it to combine with another NO2 molecule to form N2O4.

💡 3. Explanation

NO2 is a nitrogen dioxide molecule featuring an unpaired electron, which makes it paramagnetic. This unpaired electron allows interaction with another NO2 molecule to form a stable dimer, specifically N2O4, through the reaction:
2 NO2 ⇌ N2O4
This dimerization process stabilizes the odd electron condition by forming a diamagnetic compound, where electrons are paired.

❌ 4. Option Analysis

  • •Option A: N2O (Nitrous oxide) does not have unpaired electrons and is stable, therefore it does not dimerize.
  • •Option C: N2O3 (Dinitrogen trioxide) is a balanced stable compound that does not dimerize.
  • •Option D: N2O5 (Dinitrogen pentoxide) is robust against dimerization under standard conditions.
⚡

NDA Speed-Run / Mnemonic Shortcut

Remember that molecules containing an odd electron, like NO2, often form dimers to stabilize via electron pairing.

🎯

5. Key Takeaways

Nitrogen oxides with odd unpaired electrons, like NO2, have a tendency to form dimers (N2O4).

6. Visual Suggestion

Visual representation can include Lewis structures of NO2 displaying the unpaired electron and the resultant N2O4 dimer showing paired electrons, highlighting the dimerization process effectively.

Question 3 of 3 NDA MCQ

 Dinitrogen (N₂) and dioxygen (O₂) are the main constituents of air but they do not react with each other to form oxides of nitrogen because

Detailed Explanation

Correct Answer

✓ Option (c) is correct. The reaction is endothermic and requires very high temperature.

📖 Governing Law / Core Concept

The reaction between dinitrogen (\(N_2\)) and dioxygen (\(O_2\)) to form nitric oxides (\(NO\) or \(NO_2\)) is represented as:

\[N_2 + O_2 \xrightarrow{\text{High Temp}} 2NO\]

This reaction is endothermic, requiring energy input to proceed.

🧪 Step-by-Step Breakdown

The reaction proceeds at high temperatures, such as in combustion engines or lightning strikes, where the energy is sufficient to break the strong triple bond in \(N_2\).

  • The bond dissociation energy of \(N \equiv N\) is approximately 941 kJ/mol.
  • Activation energy must be provided to initiate the reaction.
  • Without the necessary temperature, \(N_2\) and \(O_2\) remain inert.

🔍 Option Analysis

  • A: The reaction does require a catalyst, but the primary barrier is temperature.
  • B: Oxides of nitrogen can be stable under specific conditions; they do not intrinsically exhibit instability.
  • D: The air composition does not hinder the reaction specifically; rather, lack of adequate energy is the issue.

⚡ Mnemonic / Speed-Run

Remember: "High Energy = Reactivity" to recall that nitrogen and oxygen need significant energy to react.

📖 Factual Verification & Reference

📖 Factual Verification & Reference:

Verified against NCERT Class XII Chemistry, Chapter on Chemical Thermodynamics and Kinetics.

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