Question

In the lindemann theory of unimolecular reaction it is shown that the apparent rate constant for such reaction is k_app = $\frac{K_{1}C}{1 + \alpha C}$ where C is conc. of the reactant, k₁&a are constant. The value of C for which k_app has 90% of its limiting value at C tending to infinitely large values. (given a = 9 × 10⁵) is -

• A. 10^–6 $\frac{mol}{lit}$
• B. 10^–4
• C. 10^–5
• D. 5 × 10^–5

Answer 1

Answer: (C)

10^–5

Answer 2

$k_{a} = \frac{k_{1}C}{1 + \alpha C}$ Or k_a = $\frac{k_{1}}{1/c + \alpha}$ ….(1)

Since C >> 1

k_a = $\frac{k_{1}}{9 \times 10^{5}}$

But k_a shows 90% of its limiting value so

k_a =$\frac{k_{1}}{10^{6}}$

Putting values in (1) Ž C = 10^–5