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### 15.23 b

Posted: Wed Mar 07, 2018 9:27 pm
Why is the formula used for this question ln[A]0 / [A]t , instead of ln [A]t/[A]0?

### Re: 15.23 b

Posted: Wed Mar 07, 2018 9:42 pm
I used the equation $ln\frac{[A]t}{[A]0} = -kt$ and got the same answer as the solutions manual. I think the two equations are equivalent because of the negative sign I used in my answer, when transferred to the other side, would flip the two concentrations.

### Re: 15.23 b

Posted: Fri Mar 09, 2018 4:50 pm
It's just algebraic manipulation; flipping the numerator and denominator will give you the negative log value.

### Re: 15.23 b

Posted: Fri Mar 09, 2018 10:22 pm
If you make both sides of the equation ln([A]t/[A]0) = -kt negative, you will have: ln([A]0/[A]t) = kt. Making the natural log negative flips the content because:
ln([A]t/[A]0) = ln[A]t - ln[A]0