+0

# if the half-life of an isotope is 7.6 minutes, how many grams will remain after 12.4 minutes if you started with 80 grams?

0
188
1

if the half-life of an isotope is 7.6 minutes, how many grams will remain after 12.4 minutes if you started with 80 grams?

Guest Jan 23, 2015

#1
+80941
+5

We have

40 = 80e^(7.6k)    solve for k

divide both sides by 80

.5 = e^(7.6k)    take the ln of both sides

ln.5 = lne^(7.6k)  and we can write

ln.5 = (7.6k)lne    and lne = 1

ln.5 = 7.6k  divide both sides by 7.6

ln.5/7.6 = k = about -.0912

So, after 12.4 minutes, we have

80e^(12.4 * -.0912) = about 25.82 g

CPhill  Jan 23, 2015
Sort:

#1
+80941
+5

We have

40 = 80e^(7.6k)    solve for k

divide both sides by 80

.5 = e^(7.6k)    take the ln of both sides

ln.5 = lne^(7.6k)  and we can write

ln.5 = (7.6k)lne    and lne = 1

ln.5 = 7.6k  divide both sides by 7.6

ln.5/7.6 = k = about -.0912

So, after 12.4 minutes, we have

80e^(12.4 * -.0912) = about 25.82 g

CPhill  Jan 23, 2015

### 20 Online Users

We use cookies to personalise content and ads, to provide social media features and to analyse our traffic. We also share information about your use of our site with our social media, advertising and analytics partners.  See details