Chemistry Reaction Kinetics ETEA 2022
PMDC Verified Question 34 of 80
The thermal decomposition of nitrogen pentaoxide in gaseous state follows. Which one of the following order of reaction? \( \text{N}_{2}\text{O}_{5(g)} \xrightarrow{\text{heat}} \text{N}_{2}\text{O}_{4(g)} + \frac{1}{2}\text{O}_{2(g)} \)
A
First order
B
Second order
C
Fractional order
D
Third order
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: First order
Concept:

The thermal decomposition of dinitrogen pentoxide (\( \text{N}_{2}\text{O}_{5} \)) is a classic textbook example of a reaction whose kinetics are experimentally determined.

Formula:

$$ \text{Rate} = k[\text{N}_{2}\text{O}_{5}]^{1} $$

Solution:

  • Despite the stoichiometry, experiments show that the half-life of this specific decomposition is completely independent of the initial concentration of \( \text{N}_{2}\text{O}_{5} \).
  • A concentration-independent half-life is the definitive hallmark of a strict first-order reaction.


Why other options are incorrect:

One might incorrectly assume an order based on intermediate mechanisms, but experimental data universally confirms it follows first-order kinetics.

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