In Lindemann theory of unimolecular reactions, it is shown that the apparent rate constant for such a reaction is k_app = (k1 C) / (1 + α C), where C is the concentration of the reactant, k1 and α are

Question

In Lindemann theory of unimolecular reactions, it is shown that the apparent rate constant for such a reaction is k_app = (k1 C) / (1 + α C), where C is the concentration of the reactant, k1 and α are constants. The value of C for which k_app has 90% of its limiting value at C tending to infinitely large is (α = 9 × 10^5)

Prashant Kotian · Accepted Answer

Correct answer: C. The limiting rate constant k_inf as C → ∞ is k1/α. Set k_app = 0.9 × (k1/α). (k1 C) / (1 + αC) = 0.9 k1 / α. This simplifies to αC / (1 + αC) = 0.9, leading to αC = 9. Given α = 9 × 10^5, C = 9 / (9 × 10^5) = 10^-5 M. Therefore, correct answer is C.

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