🤓 Based on our data, we think this question is relevant for Professor McAbee's class at CSULB.

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

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:

$\overline{){\mathbf{ln}}{{\mathbf{\left[}}{\mathbf{A}}{\mathbf{\right]}}}_{{\mathbf{t}}}{\mathbf{=}}{\mathbf{-}}{\mathbf{kt}}{\mathbf{+}}{\mathbf{ln}}{{\mathbf{\left[}}{\mathbf{A}}{\mathbf{\right]}}}_{{\mathbf{0}}}}$

where:

**[A] _{t}** = concentration at time t

**k** = rate constant

**t** = time

**[A] _{0}** = initial concentration