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Question #44845

Difficulty: 8/10 | 🟢 Free

The Question

A gaseous compound AA containing a radioactive isotope undergoes two simultaneous parallel first-order processes at 298 K298\text{ K}: a chemical decomposition A(g)→C(g)A(g) \rightarrow C(g) with a rate constant kc=2.0×10−4 s−1k_c = 2.0 \times 10^{-4}\text{ s}^{-1}, and a nuclear α\alpha-decay transforming the isotope in AA to form a new species B(g)B(g) with a decay constant λ=2.0×10−4 s−1\lambda = 2.0 \times 10^{-4}\text{ s}^{-1}. The chemical decomposition has a temperature coefficient μ=3\mu = 3 (the rate triples for every 10 K10\text{ K} rise). If the system is heated to 318 K318\text{ K} and allowed to react until AA is completely exhausted, what is the mole fraction of BB in the final product mixture?

Options

  • A.

    0.10

  • B.

    0.50

  • C.

    0.14

  • D.

    0.90

Check Your Answer

Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Exception_Exposure

Learn to identify edge cases and boundary exceptions that JEE examiners hide in math problems.

Concepts Behind This Question

Radioactive Decay as Kinetics|Temperature Coefficient (Q10)|Activation Energy Trap

Why This Question Is Tricky

Common Mistakes

This problem tests the fundamental distinction between chemical kinetics and nuclear kinetics.

Students often blindly apply the temperature coefficient (Q10Q_{10} rule) to all rate constants provided in a problem.

The 'Hidden Variable' here is the nature of the activation energy: chemical reactions have an activation barrier (Ea>0E_a > 0), making them temperature-dependent, whereas radioactive decay is a stochastic nuclear process with no thermal activation barrier (Ea=0E_a = 0), rendering its decay constant (λ\lambda) invariant to temperature changes.

Failing to recognize this exception leads to the incorrect assumption that both rates increase equally, yielding a mole fraction of 0.50.

Quick Facts About This Question

Question Information

SubjectChemistry
ChapterChemical Kinetics - Class 12
ConceptRadioactive Decay as Kinetics
Difficulty8
Cognitive Load7
Target Solve Time160 sec
AccessFree