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# First Order Kinetics Question? Watch

1. Can someone explain what the components of the equation (C = C0e-kt) are please? I've searched google but I can't find anything.

Q) After a one year storage period, an aqueous drug solution with an initial concentration of 5% (w/v) was shown by analysis to have a concentration of 45 g L-1. The drug solution is known to be ineffective if it decomposes to 70% of the initial concentration.

Assuming first order kinetics of decomposition (C = C0e-kt), calculate the shelf life (in months) of the drug solution.

Thank you
2. C is the concentration of the species, C0 is the initial concentration, k is the rate constant, and t is the time.

Hope that helps!
3. I don't really get how to work it out?
4. (Original post by Princess Kawaii)
I don't really get how to work it out?
Same format as the beer lambert law but length is replaced with time and intensity is replaced by concentration.
5. (Original post by Princess Kawaii)
I don't really get how to work it out?
Hmmm I'm not sure either, seems you are missing what the rate of decomposition is?
Hmmm I'm not sure either, seems you are missing what the rate of decomposition is?
No, we have initial concentration and the concentration after 1 year
7. (Original post by JMaydom)
No, we have initial concentration and the concentration after 1 year
Ah yeah, serves to read the question properly!

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Updated: April 1, 2013
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