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Time to reduce the reactant to one-twentieth from the first order rate constant

The same question, asked 2 times: 11 Apr 2026 S1*, 12 May 2026 S2. Every wording below, oldest first.

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  1. Question 1

    11 Apr 2026 S1

    28
    The rate constant for a first order reaction is 60 s−160\ \mathrm{s^{-1}}. How much time will it take to reduce the concentration of the reactant to 1/20th1/20^{th} of its initial value?

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  2. Question 2

    12 May 2026 S2

    27
    Rate constant for first order reaction is 40 s−140\,s^{-1}. Calculate the time required to reduce the concentration to 1/201/20 th of its initial value.

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