## How to solve for time, given k and concentrations

$aR \to bP, Rate = -\frac{1}{a} \frac{d[R]}{dt} = \frac{1}{b}\frac{d[P]}{dt}$

Katie Clark 3B
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Joined: Fri Sep 25, 2015 3:00 am

### How to solve for time, given k and concentrations

How do you solve for time given k and the concentrations. For example, in the Winter 2014 Quiz 2 Prep #9, the question is: A reaction has k=8.39 M-1s-1. How long does it take for the reactant concentration to drop from 0.0840 M to 0.0220 M?

Jake Ney lecture 1 discussion 1F
Posts: 26
Joined: Fri Sep 25, 2015 3:00 am

### Re: How to solve for time, given k and concentrations

Because the he K value is given in M-1s-1 we know that we are dealing with a 2nd order reaction. Solving the question now is just a matter of plugging in the given values into the equation 1/[A]=kt+1/[Ao] => 1/[.0220 M]=(8.39M-1s-1)t+1/[.0840 M] and solving algebraically for t.