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The half life period of a first order chemical reaction is 6.93 minutes. The time required for the completion of 99% of the chemical reaction will be (log 2 = 0.301)

1. 23.03 minutes
2. 46.06 minutes
3. 406.6 minutes
4. 230.03 minutes

Correct answer: 46.06 minutes

Solution

k = 0.693/6.93 = 0.1 per min. For 99% completion, t = (2.303/k)*log(100/1) = (2.303/0.1)*2 = 46.06 minutes.

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