Half-life for First and Second Order Reactions For a first-order reactant concen
ID: 562614 • Letter: H
Question
Half-life for First and Second Order Reactions For a first-order reactant concentration. It is expressed as reaction, the half-life is constant. It depends only an the rate constant k and not on the 0.693 1/2 For a second order raction,the hai to deperds on the rade constant and the concentration of the The half-life of a reaction, ti/a, is the time it takes for the reactant concentration [A] to decrease by half. For example, after one half-ife the concentration falls from the inital concentration reactant and so is expressed as t1/2 = A after a third half-life to [Alo/8, and so on. on. Part A Acertan frst-order reacion (A products) has a rate constant of 1.00x 10-2 s-1 at 45°C. How many minutes does it take for the concentration of the reactant. [A.todropb625%ofthe original Express your answer with the appropriate units View Available Hint(s) 0.78 min Submit Prevlous Answers Request Answer Incorrect; Try Again: 2 attempts remainingExplanation / Answer
A)
use,
ln([A]/[0]) = -k*t
given,
[A]/[A0] = 0.25
k = rate constant
= 1.00*10^-2 s^-1
so,
ln(0.25) = -1.00*10^-2*t
-1.39 = -1.00*10^-2*t
t = 139 s
Answer : 139 s
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