Using ln[A]


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Cynthia Ulloa
Posts: 52
Joined: Fri Feb 23, 2018 3:02 am

Using ln[A]

Postby Cynthia Ulloa » Thu Mar 07, 2019 11:52 am

Can someone explain to me why we would use ln[A] instead of [A] like we do for the rest of the orders?

Andrea Zheng 1H
Posts: 61
Joined: Fri Sep 28, 2018 12:26 am

Re: Using ln[A]

Postby Andrea Zheng 1H » Thu Mar 07, 2019 12:05 pm

You would use ln[A] for first order reactions. For these reactions, rate=k[A]=-1/a * d[A]/dt. If you set a=1 and then you separate the variables, you get k*dt=-d[A]/[A] or (-1/[A])*d[A]. If you integrate both sides, you would get kt=-ln[A], or -kt=ln[A], as the integral of (-1/[A])*d[A] is ln[A]. This is why you use the ln[A] for first order reactions.

gwynlu1L
Posts: 62
Joined: Fri Sep 28, 2018 12:19 am

Re: Using ln[A]

Postby gwynlu1L » Fri Mar 08, 2019 1:12 am

as a general idea, you use [A] for zero order, ln[A] for first order, and 1/[A] for second order


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