Assertion (A) : The molecularity of the given reaction is 2.
\( 2\text{HI} \longrightarrow \text{H}_2 + \text{I}_2 \)
Reason (R) : Two molecules of the reactants are involved in simultaneous collision between them.
\( 2\text{HI} \longrightarrow \text{H}_2 + \text{I}_2 \)
Reason (R) : Two molecules of the reactants are involved in simultaneous collision between them.
Show Hint
- 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 A
Solution and Explanation
• Unimolecular: One molecule decomposes or rearranges.
• Bimolecular: Two species collide simultaneously.
• Termolecular: Three species collide simultaneously (rare).
Step 1: Analyzing the chemical equation provided.
The reaction given is the decomposition of hydrogen iodide: \[ 2\text{HI} \longrightarrow \text{H}_2 + \text{I}_2 \] In this elementary process, two molecules of hydrogen iodide (HI) must come together and collide with sufficient energy and proper orientation to break the existing \(\text{H}-\text{I}\) bonds and form \(\text{H}-\text{H}\) and \(\text{I}-\text{I}\) bonds.
Step 2: Linking stoichiometry to molecularity.
Since the stoichiometric coefficient of HI in the elementary step is 2, and no other reactants are involved, exactly two molecules are required for the collision. This makes the molecularity of the reaction equal to 2 (bimolecular). Therefore, the Assertion (A) is True.
Step 3: Evaluating the Reason.
The Reason states that two molecules are involved in a simultaneous collision. This is the fundamental definition of why a reaction is termed "bimolecular" or has a molecularity of 2. Thus, the Reason is True and it successfully explains the Assertion. Final Answer: The correct choice is (A).
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- Assertion (A): The molecularity of the given reaction is 2
$2HI \longrightarrow H_2 + I_2$
Reason (R): Two molecules of the reactants are involved in simultaneous collision between them. - Identify the correct statement :
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