1. A first-order decomposition reaction has a rate constant of 0.0056 yr^-1. How
ID: 503608 • Letter: 1
Question
1. A first-order decomposition reaction has a rate constant of 0.0056 yr^-1. How long does it take for [reactant] to reach 12.5% of its original value? Be sure to report your answer to the correct number of significant figures.
____yr
2. In a first-order decomposition reaction, 50.0% of a compound decomposes in 12.0 min.
a)What is the rate constant of the reaction? (round to four decimal places)
k=____min^-1
b)How long does it take for 83.0% of the compound to decompose? (round to one decimal place)
t=____min
Explanation / Answer
1)
K = 0.0056 yr-1
[Ao] =100
[A] =12.5 % of [Ao] = 12.5
t= ?
use integrated rate law for 1st order reaction:
ln [A] = –kt + ln [A]o
ln (12.5) = -0.0056*t + ln (100)
0.0056*t = 2.079
t = 371 yr
Answer: 371 yr
i am allowed to answer only 1 question at a time
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