The mass, q, of a sample of tritium (a radioactive isotope of hydrogen), decays at a rate of 5.626% per year. given a quantity of 726 grams, determine the graph that best models the decay of this radioactive substance.

To make a plot, you have to establish which is the independent and dependent variable. The independent variable (x-axis) is time in years; the dependent variable (y-axis) is mass of tritium in grams.Then, you create a formula.

At year 1,
726(1 - 0.05626) = 685.16 g

At year 2,
685.16 (1 - 0.05626) = 646.61 g

At year 3,
646.61 g (1 - 0.05626) = 610.23 g

and so on and so forth. It is easier to use MS Excel for this step. The final graph is shown in the picture. In ten years' time, the mass of tritium would be 406.87 g. That's almost half of the original mass.