Posted by **Madison** on Wednesday, May 25, 2011 at 1:51pm.

Will you check this answer for me?

the half-life of strontium-87 is 2.8hr. What percentage of this isotope will remain after 8 hours and 24 minutes?

?? 34%

- Chemistry -
**DrBob222**, Wednesday, May 25, 2011 at 4:34pm
I'd be interested in knowing how you came up with that answer.

8 hr and 24 min, according to my calculation is [(8*60)+24/60] = 8.4 hrs.

k = 0.693/t_{1/2} = 0.693/2.8 = 0.2475

ln(No/N) = kt

I took No = 100 (an arbitrary number)

Solved for N

k from above

t = 8.4

Solving for N, I obtained 12.5 so if we started with 100 g at time = zero, then at the end of 8.4 hours we would have 12.5 g left. %left = (12.5/100)*100 = ??

Check my work.

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