15.27 vs 15.35


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Justin Chu 1G
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Joined: Thu Jul 13, 2017 3:00 am
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15.27 vs 15.35

Postby Justin Chu 1G » Wed Mar 07, 2018 11:25 pm

For the homework problems, I noticed that in 15.27 (first-order reaction), you could simply calculate how many half lives have occurred and multiply the number by the half-life (ex: 1/8 of the original concentration would equal (1/2)^3 so you could multiply the half life by 3). However, I noticed that in 15.35 (second-order reaction), I couldn't simply do the same thing. Is there a specific reason why?

Manvir2K
Posts: 32
Joined: Fri Sep 29, 2017 7:05 am

Re: 15.27 vs 15.35

Postby Manvir2K » Thu Mar 08, 2018 12:48 pm

This method works for 27 because it is in first order, while 35 is in second order. I think calculating the half lives that have occurred and multiplying the number by the half-life only works for 1st order.

Gwyneth Huynh 1J
Posts: 30
Joined: Fri Sep 29, 2017 7:05 am

Re: 15.27 vs 15.35

Postby Gwyneth Huynh 1J » Thu Mar 08, 2018 3:58 pm

I agree! For first order reactions, the half life is independent of initial concentration. However, for second order reactions, the half life depends on initial concentration.

Jennie Fox 1D
Posts: 66
Joined: Sat Jul 22, 2017 3:01 am

Re: 15.27 vs 15.35

Postby Jennie Fox 1D » Thu Mar 08, 2018 4:20 pm

This is because in second order reactions, half life depends on initial concentration, whereas half life in first order reactions does not depend on concentration.


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