First slide
First order reactions
Question

The rate of first-order reaction is 0.04 mol L-1S-1 at 10 seconds and 0.03 molL-1S-1  at 20 seconds after initiation of the reaction. The half-life period of the reaction is

Moderate
Solution

 For a first order reaction, A Products  and  for concentration of the reactant at two different times,

k=2.303t2-t1log[A]1[A]2

 k=2.303t2-t1log( rate )1( rate )2 ( rate [A])

k=2.303(20-10)log0.040.03=0.0287sec-1

t1/2=0.693k=0.6930.0287sec-1=24.14sec

 

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