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Homework question

Posted: Mon Mar 11, 2019 7:36 pm
by sarahtang4B
On 7B3b, its a first order reaction so how is it ln(A0/At) = kt and not -kt? I thought it was -kt for first order reactions?

If not, how did we get that equation?

Re: Homework question

Posted: Mon Mar 11, 2019 7:43 pm
by Henry Krasner 1C
This is a different way to display the first order reaction equation.
You start with
ln[A]=ln[A(initial)] - kt
Then you move ln[A(initial)] to the other side and use log rules to get
ln([A]/[A(initial)])=-kt.
Then divide by -k or -t depending on what you want to find.

The textbook just organizes it differently, but either method will allow you to obtain the same result.

Re: Homework question

Posted: Tue Mar 12, 2019 11:31 pm
by Lia Inadomi 1I
This is because it is ln([A]0/[A]t) instead of ln([A]t/[A]0) which is when it would be -kt. This is just because of log rules so ln([A]t/[A]0)=-ln([A]0/[A]t) because coefficient of a log can be seen as the exponent inside the log function