A first-order reaction has a hall-life of 21.3s. How long does it take for the concentration of the reactant in the reaction to fall to one-eighth of its initial value?

1 Answer
Al E.
Nov 23, 2017

It would take approximately #64.0s# given those data.

Explanation:

#21.3s = 0.693/k#
#therefore k approx 3.25*10^-2s^-1#

#ln(1/8) = -3.25*10^-2s^-1 * t#
#therefore t approx 64.0s#

Each equation I used is assuming this reaction's kinetics are of the first order, which is cited. The first equation is a simplified version for the half life of a first order reactant, and the second equation is the general equation for first order reactions in chemical kinetics.

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