Assertion (A) : For complex reaction, order of reaction is given by the slowest step.
Reason (R) : Order of a reaction is an experimental quantity.
Reason (R) : Order of a reaction is an experimental quantity.
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If a reaction is elementary, its order and molecularity are usually the same.
- Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
- Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
- Assertion (A) is true, but Reason (R) is false.
- Assertion (A) is false, but Reason (R) is true.
The Correct Option is B
Solution and Explanation
• A complex reaction is one that proceeds through a sequence of elementary steps (a mechanism).
• The Rate Determining Step (RDS) is the slowest step in the mechanism, which controls the overall rate of the reaction.
• The order of a reaction is the sum of exponents of the concentration terms in the rate law expression.
Step 1: Evaluate the Assertion
In any multi-step process, the overall speed is limited by the slowest component.
For a chemical reaction, the rate law (and thus the order) is derived from the stoichiometry of the slowest elementary step.
Therefore, Assertion (A) is true.
Step 2: Evaluate the Reason
Unlike molecularity (which is theoretical), the order of a reaction cannot be determined simply by looking at the balanced equation of a complex reaction.
It must be determined through experimental observations of how the rate changes with concentration.
Therefore, Reason (R) is also true.
Step 3: Check for the logical connection
Does the fact that "Order is experimental" explain why the slowest step determines the order?
No. The reason the slowest step determines the order is because it acts as a kinetic bottleneck.
The experimental nature of order is a separate characteristic of chemical kinetics.
Step 4: Conclusion
Both statements are true, but there is no "because" relationship between the Reason and the Assertion. The final answer is (B).
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- Write IUPAC names of the following coordination entities:
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