Chemical Kinetics Question 45

Question: The reaction, $ X\to $ product follows first order kinetics. In 40 minutes the concentration of X changes from 0.1 M to 0.025 M Then the rate of reaction when concentration of X is 0.01 M

Options:

A) $ 1.73\times {10^{-4}}M\ {{\min }^{-1}} $

B) $ 3.47\times {10^{-5}}M\ {{\min }^{-1}} $

C) $ 3.47\times {10^{-4}}M\ {{\min }^{-1}} $

D) $ 1.73\times {10^{-5}}M\ {{\min }^{-1}} $

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Answer:

Correct Answer: C

Solution:

Concentration will fall from 0.1 M concentration to 0.025 M concentration within 2 half lives.

$ 2\times {T_{1/2}}=40 $ min
$ \therefore \ \ {T_{1/2}}=20 $ min Rate of reaction = K . c $ =\frac{0.693}{{T_{1/2}}}.c $

$ =\frac{0.693}{20}\times {10^{-2}}M/\min $

$ =3.47\times {10^{-4}}M/{{\min }^{-1}} $ .



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