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posted by  wvufan2211 on 2/21/2008 9:39:20 PM  |  status: Closed  

half life problem

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Question Details:
The nuclear transmutation reaction, X  --> products, is a first order reaction. If the half-life of X is 188.5 hours, how much would a sample weighing 14.55 mg today weigh at the same time tomorrow?

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posted by CHEMNATION! on 2/21/2008 9:42:59 PM  |  status: Live
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wvufan2211's comment:
"great...thanks"
Response Details:
ln(x/14.55) = - (0.693/188.5 h-1)(24 h)
x = 14.55 * exp(- (0.693/188.5 h-1)(24 h))=13.32 mg left
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posted by Clark on 2/21/2008 10:01:20 PM  |  status: Live
Asker's Rating: Helpful   
wvufan2211's comment:
"thanks! that helps a lot"
Response Details:
In order to do this question you need to use the half - life formula:
 
AL = AO(1/2)t/n
AL represents your final weight, in this question it will be the weight of the substance tomorrow, AO represents your initial weight - in this question it is 14.55mg, t represents your time - in this question it will be 24 hours because it is asking for the weight tomorrow, and 'n' represents your half life - which is 188.5 hours in this question.
All you have to do is plug those numbers into your equation and solve for AL:
AL = 14.55(1/2)24/188.5
= 13.32mg
 
I hope this helps!!
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