A person takes a single dose of 500 mg of aspiring. The half life of aspirin in the body is 3 hours. At what point will 97% of the aspirin have left the person’s body?

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1 Answer
Al E.
Dec 8, 2017

Unless a problem states otherwise, I would assume it is a first order rate of decay. Hence, we would use the first order equations that illustrate and relate kinetics,

t_(1/2) = 0.693/k

ln""([A]_t)/([A]_0) = -kt

The rate constant is,

3h = 0.693/k
therefore k approx 0.231h^-1

Subsequently we may realize the amount of time this process takes with our knowledge of its kinetics; it takes,

ln((1-0.97)/1) = -0.231h^-1*t
therefore t approx 15.2h

for that quantity of aspirin to have "left" the body.

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