### Half-Life 1st Order Reaction

Posted:

**Wed Mar 06, 2019 10:44 am**Is the equation t1/2 = 0.693/k valid for all first order reactions? And if so, it it because the initial concentration of A cancel out and leave ln(1/2)?

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=148&t=43696

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Posted: **Wed Mar 06, 2019 10:44 am**

Is the equation t1/2 = 0.693/k valid for all first order reactions? And if so, it it because the initial concentration of A cancel out and leave ln(1/2)?

Posted: **Wed Mar 06, 2019 12:39 pm**

Yes, that's exactly correct.

Posted: **Thu Mar 07, 2019 12:19 pm**

Also remember that you can always derive this equation it you have any doubts

Posted: **Thu Mar 07, 2019 1:30 pm**

For the first order

the half life equation is t(1/2)= ln2/k.

It is applicable to all first order rate reactions.

the half life equation is t(1/2)= ln2/k.

It is applicable to all first order rate reactions.

Posted: **Sat Mar 09, 2019 2:50 pm**

Why is it that the half-life of a first order reaction doesn't depend on initial concentration?

Posted: **Sat Mar 09, 2019 11:14 pm**

Yes, it is applicable to all first order rate reactions.

Posted: **Sat Mar 09, 2019 11:21 pm**

The initial concentration gets cancelled out when you derive the equation. Thus you end up with the equation t1/2 = 0.693/k