If the half-life of technitium-104 is 18.0 min, how much of a 14.2-g sample will remain after 72 minutes?

3.55g

1.78g

0.888g

0.444g

The decay of a radioactive isotope can be predicted using the formula: A = Ao[2^ (-t/T_0.5) ] where A is the amount after time t, Ao is the original amount and T_0.5 is the half-life. Using the equation and the given values, 0.888 g of the sample will remain after 72 minutes.