Question

For a first-order reaction, the half-life is constant. It depends only on the rate constant k and not on the reactant concentration. It is expressed as t1/2=0.693k For a second-order reaction, the half-life depends on the rate constant and the concentration of the reactant and so is expressed as t1/2=1k[A]0

Part A

A certain first-order reaction (A→products) has a rate constant of 7.50×10−3 s−1 at 45 ∘C. How many minutes does it take for the concentration of the reactant, [A], to drop to 6.25% of the original concentration?

Part B

A certain second-order reaction (B→products) has a rate constant of 1.10×10−3 M−1⋠s−1 at 27 ∘C and an initial half-life of 204 s . What is the concentration of the reactant B after one half-life?