In your lab you are studying the kinetics of the degradation of a pain killer in
ID: 697354 • Letter: I
Question
In your lab you are studying the kinetics of the degradation of a pain killer in the human liver. You are monitoring the concentration of the pain killer over a period of time. The initial concentration of the pain killer in your experiment was 1.85 M. After 12.06 hours the concentration was found to be 0.9250 M. In another 6.030 hours the concentration was found to be 0.4625 M (t 18.09 hours overall) If another experiment were set up where the initial concentration of the pain killer was 0.325 M, how long would it take for the pain killer concentration to reach 0.0123 M? (in hours) 42.7 4.73 3.59 1.02E+03 4.08Explanation / Answer
Initial concentration = 1.85 M
After 12.06 hrs concentration = ( 1.85 / 2) = 0.925 M half of the initial concetration
It means 12.06 hrs is half life
After 6.03 hrs , the concetration = 0.4625 M ( 0.925/2) half of the concetration after first half life
So
Here time of half life decreases with concentration over time.
It means Half life is proportional to concentration
So it is zero order kinetics where ,
t1/2 = [Ao] / 2k
[Ao] = initial concentration
k = rate constant
k = [Ao] / (2t1/2) = 1.85 / (2*12.06) = 0.0767 M/hr
Zero order rate law :
At = Ao - kt (At = concentration at time t )
0.0123 = 0.325 - 0.0767*t
t = 4.08 hours
Answer is 4.08 hours