A biochemist studying the breakdown in soil of the insecticide DDT finds that it decays by a first-order reaction with a half-life of 12 yr. How long does it take DDT to decay from 305 ppbm to 17 ppbm in a soil sample ("ppbm" is parts per billion by mass)?
2007-12-08 08:37:46 · 3 answers · asked by socr8711 2 in Science & Mathematics ➔ Chemistry
in twelve years 305 will decay to half of that, which is 152.5, and every twelve years that number will half again, so just keep going untill you find out how many years will be needed before 17 is reached.
I can understand why you might struggle, because this is more of a physics question.
2007-12-08 08:45:25 · answer #1 · answered by honourableone 3 · 0⤊ 0⤋
(17/305) = (2 to the x/12 power)
Solve for x.
2007-12-08 16:53:44 · answer #2 · answered by Tim C 7 · 0⤊ 0⤋
Half life 12 years so
305 after 12 years = 152.5
another 12 years = 76.25
another 12 years = 38.125
another 12 years = 19.0625
so approx 49 years
2007-12-08 16:51:17 · answer #3 · answered by Anonymous · 0⤊ 0⤋