Question

You have found a mysterious substance that appears to be radioactive. You take a sample to a nuclear chemist who measures out 100 g. of the substance. Thirty hours later, the chemist tests the sample and finds that 6.25 grams of the sample remains radioactive. What is the half-life of the sample?

a. 4 hours
b. 7.5 hours
c. 15 hours
d. 30 hours

Answer 1

First of all this really belongs to the chem section, but I think you will be fine cuz lots of biologists are also chemists

Answer 2

Draw a schematic of what's going on will help you

Answer 3

As you can see, it takes a total of 4 hl to get from 100 to 6.25

Answer 4

therefore: 4t=30, t=7.5

Answer 5

got it?

Answer 6

yup thanks!