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Question #44691

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The Question

Consider an anion $R$ , which is the conjugate base of a weak acid and is isoelectronic with ozone ( $\ce{O3}$ ). $R$ is completely oxidized by $\ce{KMnO4}$ in a neutral aqueous medium at $298\text{ K}$ . Let the balanced chemical equation for this redox reaction, reduced to the simplest whole-number coefficients, have the stoichiometric coefficients $x$ for $\ce{KMnO4}$ and $y$ for $R$ .

In a separate kinetic study, a hypothetical reaction is found to follow the rate law: $\text{Rate} = k[A]^x[B]^y$ . What are the correct units for the rate constant $k$ ?

Options

A.
$\text{L}^4 \cdot \text{mol}^{-4} \cdot \text{s}^{-1}$
B.
$\text{L}^6 \cdot \text{mol}^{-6} \cdot \text{s}^{-1}$
C.
$\text{L}^2 \cdot \text{mol}^{-2} \cdot \text{s}^{-1}$
D.
$\text{L}^5 \cdot \text{mol}^{-5} \cdot \text{s}^{-1}$

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Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Numerical_Precision

Improve calculation stamina and avoid rounding errors in high-stakes competitive examinations.

Concepts Behind This Question

Isotopes-Isobars-Isotones-Isoelectronic|KMnO₄ Redox pH Dependency|Units of Rate Constant (k)

Why This Question Is Tricky

Common Mistakes

This problem tests the student's ability to bridge subatomic properties (isoelectronic species identification) with macroscopic redox stoichiometry and chemical kinetics.

The primary 'Chemical Exception/Trap' is the pH-dependency of the $\ce{KMnO4}$ n-factor.

Students habitually default to the acidic medium n-factor (5) for $\ce{KMnO4}$ , which would yield $x=2, y=5$ , an overall reaction order of 7, and the incorrect units of $\text{L}^6 \cdot \text{mol}^{-6} \cdot \text{s}^{-1}$ (Option B).

It requires precise knowledge that in neutral/faintly alkaline media, permanganate reduces to $\ce{MnO2}$ (n=3).

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Structure of Atom - Class 11 Part 1
Concept	Isotopes-Isobars-Isotones-Isoelectronic
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free