math
posted by Matthew on .
A quantity of oxygen gas had 16.32 g of the radioactive isotope oxygen19 in it. When measured exactly 10 minutes later, the amount of oxygen19 was 0.964 g. What is the halflife, in seconds, of oxygen19?

16.32(1/2)^(t/k) = .964 , where t is in minutes, and k is the halflife in minutes.
(.5)^(10/k) = .0590686.. ( I stored it)
ln both sides
(10/k) ln .5= ln (.059068...)
10/k = 4.081464...
k = 2.4504 minutes or 147.006 seconds