The integrated rate law allows chemists to predict the reactant concentration af

Question

The integrated rate law allows chemists to predict the reactant concentration after a certain amount of time, or the time it would take for a certain concentration to be reached. The integrated rate law for a first-order reaction is: [A]=[A]0ekt Now say we are particularly interested in the time it would take for the concentration to become one-half of its initial value. Then we could substitute [A]02 for [A] and rearrange the equation to: t1/2=0.693k This equation calculates the time required for the reactant concentration to drop to half its initial value. In other words, it calculates the half-life.

Part A

What is the rate constant of a first-order reaction that takes 536seconds for the reactant concentration to drop to half of its initial value?

Express your answer with the appropriate units.

Part B

A certain first-order reaction has a rate constant of 8.90

Explanation / Answer

For first-order reaction:

A) t1/2 = 0.693 / k

or 536 = 0.693 / k

or k = 0.00129 sec-1

B) A =Ao e^(-kt)

or -kt = ln(A/Ao)

or t = -1/k*ln(A/Ao)

So, here t = -(1 / 8.90

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