00:01
Here we have a first -order reaction, and why that's important, it means our t -1 -half is constant.
00:05
So with zero and third -order, second -order reactions, your t -1 -half will change with concentration, but here in first order, it does not, it stays constant at 60 minutes.
00:15
And so t -1 -half being our half -life.
00:18
Your initial concentration in the bloodstream is one microgram per mil -liter, and the time we're interested in that has elapsed is 300 minutes.
00:29
What is going to be the concentration in the bloodstream? well, when we're thinking of half -life, what it means is if our initial concentration is one microgram per liter, a milliliter, after 60 minutes, one half of it has decayed or decomposed.
00:51
So at one half -life, so we'll do an arrow, 60 minutes elapse, and our end concentration is 0 .5 micrograms per millilater.
01:04
And then another half -life, another 60 minutes.
01:07
We divide that value again, and we get 0 .25 -5 micrograms per milliliter.
01:14
And so you do that, and what you might realize is if you do that five times, you'll get the answer.
01:20
The more succinctly do that, instead of writing this five separate times, is to take your one microgram per millilator, and then divide by two to the power of five...