The half life of carbon-11 is 20 minutes. A sample of carbon-11 has25mCi. How much is left after 1 hour?* A)12.5mci B)10.2mCi C)2.25mci D)3.125mci
1 hour is 3 half lives
25 x 1/2 x 1/2 x 1/2 = 3.125 mCi
