00:01
Hi, so for this problem, we're going to use the formula for first order reaction based on half -life, and that's going to be why the remaining amount of the substance is equivalent to the initial amount multiplied by 2 -rays the problem negative t, the time elaps over the half -life.
00:24
Okay, so using this equation, we'll solve for the first one.
00:27
We have the remaining amount that's our unknown the initial amount is two point or two raised the verb 604 atoms and then two multiplied by negative t which is 12 .3 years and then the half life is also 12 .3 years so we'll be able to cancel years in here and our answer for this will be equivalent to 9 .202 times 10 to the 18, this is atoms.
01:08
Oh, sorry.
01:15
Now for the second one, using the same equation, second one states that after 12 more years.
01:25
So our initial amount now will be our answer from a, that's 9 .22 times 10 to the 18 atoms.
01:34
And then 2 raise the power of negative, 12 .3.
01:38
Over again they have like 12 .3.
01:41
This is years, years, cancel this one...