Half life


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Abigail Menchaca_1H
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Joined: Sat Sep 07, 2019 12:19 am

Half life

Postby Abigail Menchaca_1H » Sun Mar 15, 2020 11:52 pm

Where do you start when you determine the half life for a zero order reaction?

Adam Kramer 1A
Posts: 103
Joined: Sat Aug 24, 2019 12:15 am

Re: Half life

Postby Adam Kramer 1A » Mon Mar 16, 2020 12:14 am

to find the half life of the zero order reaction, you need to use the equation [A.5]=-kt+[A0], where A.5 is half the concentration of A0
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Serena Song 1A
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Re: Half life

Postby Serena Song 1A » Tue Mar 02, 2021 9:21 pm

You could also use t1/2 = [A]0/2k!

clairehathaway 2J
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Joined: Wed Sep 30, 2020 9:38 pm

Re: Half life

Postby clairehathaway 2J » Wed Mar 03, 2021 1:31 pm

Today in lecture (3/3) Dr. Lavelle went through the derivation of finding the equation for the half-life of a zero-order reaction.
He started with the equation , then when looking for we know that . Then we can find that
which simplifies to and ultimately gives us the zero-order half life equation which is:

DMaya_2G
Posts: 103
Joined: Wed Sep 30, 2020 9:58 pm

Re: Half life

Postby DMaya_2G » Wed Mar 03, 2021 4:45 pm

You just simply use the equation t1/2 = [A]0/2k

apurva-3E
Posts: 142
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Re: Half life

Postby apurva-3E » Wed Mar 03, 2021 6:52 pm

We can use the reaction: t(1/2) = [A]0/2k

Xinying Wang_3C
Posts: 99
Joined: Wed Sep 30, 2020 9:39 pm

Re: Half life

Postby Xinying Wang_3C » Thu Mar 04, 2021 12:28 am

you could plug numbers into the equation, t(1/2) = [A]0/2k

Samantha Lee 1A
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Re: Half life

Postby Samantha Lee 1A » Thu Mar 04, 2021 11:22 am

The half life of a zero order reaction is

The derivation of this equation was in 3/3 lecture. The integrated rate law for the zero order is . At , [A] = 1/2*([A]_0). When we substitute 1/2[A]_0 into the equation for [A], the equation can be rearranged. The initial concentrations of A can be combined and then we solve for . When we solve for , we get the half life equation for the zero order.

We can either derive the equation every time you want to use the half life equation for each order, using its specific integrated rate law, or you can use the answer of the derivation. The half life equation will be the same for every problem that is of that order.

Stephen Min 1I
Posts: 95
Joined: Wed Sep 30, 2020 10:01 pm

Re: Half life

Postby Stephen Min 1I » Thu Mar 04, 2021 2:22 pm

A 0 order reaction has a half life of t = [A]/2k, which depends on [A] initial.


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