College Physics 10th Edition by Raymond Serway,Chris Vuille

Exercise 24

A radioactive sample contains 3.50 g of pure 11 C, which has a half-life of 20.4 min. (a) How many moles of 11 C are present initially (b) Determine the number of nuclei present initially. What is the activity of the sample (c) initially and (d) after 8.00 h