Problem: Barium-122 has a half-life of 2 minutes. You just obtained a sample weighing 10.0 grams. If takes 10 minutes to set up the experiment in which barium-122 will be used. How many grams of barium-122 will be left when you begin the experiment?a. 0.313 g remainb. 0.625 g remainc. 0.00 g remaind. 50.0 g remaine. 2.00 g remain 

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We’re being asked to calculate the mass of barium-122 remaining from 10.0 g Ba-122 after 10 minutes. The half-life of Ba-122 is 2 minutes.


Since barium-122 has a half-life, it is a radioactive isotope. Recall that radioactive isotopes follow first-order kinetics.


The integrated rate law for a first-order reaction is as follows:


ln[A]t=-kt+ln[A]0


where: 

[A]t = concentration at time t

k = rate constant

t = time

[A]0 = initial concentration


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Problem Details

Barium-122 has a half-life of 2 minutes. You just obtained a sample weighing 10.0 grams. If takes 10 minutes to set up the experiment in which barium-122 will be used. How many grams of barium-122 will be left when you begin the experiment?

a. 0.313 g remain

b. 0.625 g remain

c. 0.00 g remain

d. 50.0 g remain

e. 2.00 g remain 


Frequently Asked Questions

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Our tutors have indicated that to solve this problem you will need to apply the Identifying Reaction Order concept. If you need more Identifying Reaction Order practice, you can also practice Identifying Reaction Order practice problems.

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