December 22, 2024, 10:47:41 AM
Forum Rules: Read This Before Posting


« previous next »
Pages: [1]   Go Down

Topic: Half life  (Read 2891 times)

0 Members and 1 Guest are viewing this topic.

Offline UG

  • Full Member
  • ****
  • Posts: 822
  • Mole Snacks: +134/-15
  • Gender: Male
Half life
« on: May 28, 2010, 06:16:16 AM »
Hi, how does one find the half life of a reaction such as
d[Cl2]/dt = k[Cl2]1.5 ?
Does it involve integrating? If so, how :-\ ?
Logged

Offline sjb

  • Global Moderator
  • Sr. Member
  • ***
  • Posts: 3653
  • Mole Snacks: +222/-42
  • Gender: Male
Re: Half life
« Reply #1 on: May 28, 2010, 07:48:01 AM »
How would you do it, working from first principles, if it were first order?
Logged

Offline UG

  • Full Member
  • ****
  • Posts: 822
  • Mole Snacks: +134/-15
  • Gender: Male
Re: Half life
« Reply #2 on: May 28, 2010, 08:37:36 AM »
Integrate it
d[Cl2]/[Cl2] = k dt which becomes c - ln[Cl2] = kt
At t = 0 [Cl2] = [Cl2]0 and so c = [Cl2]0
Or ln([Cl2]0 / [Cl2]) = kt
After one half life [Cl2] = [Cl2]0/2
Or ln([Cl2]0 / ([Cl2]0/2)) = kt1/2
Giving ln(2) = kt1/2
and t1/2 = ln 2 /k
Logged

Offline sjb

  • Global Moderator
  • Sr. Member
  • ***
  • Posts: 3653
  • Mole Snacks: +222/-42
  • Gender: Male
Re: Half life
« Reply #3 on: May 31, 2010, 01:26:50 PM »
So follow a similar approach to the reaction order you have.
Logged
Pages: [1]   Go Up
« previous next »
Sponsored Links