Can someone help with this one? Half life of 55Cr is about 2 hours. A sample of the isotopes delivered from the reactor to lab requires 12 hours. What is the minimum amount of material that should be shipped to get 1.0 mg of 55Cr.

Question

I said 32mg but I got it wrong and I don't know why

Answer 1

You can use an equation or you could just do it intuitively; I choose to do this one intuitively.

1.0mg =12 hrs

2.0mg=10 hrs

4.0mg=8 hrs

8.0mg= 6hrs

16.0mg=4hrs

32.0mg=2hr

64.0mg=0hrs

So, you will initially need 64.0mg of 55Cr to have a minimum of 1.0mg after 12-hours.