Half-life for First and Second Order Reactions The half-life of a reaction, t1/2, is the time it takes for the reactant concentration [A] to decrease by half. For example, after one half-life the concentration falls from the initial concentration [A]0 to [A]0/2, after a second half-life to [A]0/4, after a third half-life to [A]0/8, and so on. on. For a first-ocder reaciion, the halk hite is constant. If depends only on the rate constant k and nor on the reectant ebncentration. It is arpinsed ats t1/2=k0.693 Foc a socond-order reaction, the half-ife depends on the rale constant and the concentration of the reactant end so is expressed as t1/2=A41 Part A A certain frst-order reaction (A products) has a rate constant of 3.30103s1 at 45C. How many minutes does it taka for the concentration of ine reactant, (A), to drop to 6.25% of the original concentration? Express your answer with the appropriate units- View Available Hint(s) Part B A cartain second-order reaction (B products) has a rate constant of 1.40103M1s1 at 27C and an initial halfilie of 286 s. What is ine. concentration of the reactant B atter one half-lite? For a first-order reaction, the half-life is constant. It dopends only on the rate constant k and nof on the reuctart concentralan: it is expreseed as 15 for the roactant pie, after one For a second-order reaction, the half-life depends on the rate constant and the concentration of the reactant and so is expressod as t1/2=k[]01 Part A Part B A certain second-order reaction (B products) has a rate constant of 1,40103M1,s1 at 27 . C and an inital half lee of 288 s . What is the concentration of the reactant B after one halfsife? Express your answer with the appropriate units