Chemical Kinetics Question 299

Question: A first order reaction is half-completed in 45 minutes. How long does it need for 99.9% of the reaction to be completed-

Options:

A) 20 hours

B) 10 hours

C) $ 7\frac{1}{2} $ hours

D) 5 hours

Show Answer

Answer:

Correct Answer: C

Solution:

[c] $ k=\frac{0.693}{45} $ further $ t=\frac{2.303}{0.693}\times 45\log \frac{100}{100-99.9} $

$ =\frac{2.303\times 45\times 3}{0.693}=7\frac{1}{2}hours. $



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