chemistry
posted by rachel .
a sample of sodium24 with an activity of 12 mCi is used to study the rate of blood flow in the circulatory system. If sodium24 has a halflife of 15 h, what is the activity of the sodium after 2.5 days. please show work.

1). half life = ln(2) / lambda
where lambda is the radioactive decay constant
2). A(t) = 12mCi * e ^  (lambda * t)
where t is time, A(t) is activity as a function of time
15 hr = ln2 / lambda
solve for lambda
convert 2.5 days to hours
Then t = 2.5 days * (24 hrs / day)
Plug these numbers into A(t)