## Calculating k

juleschang16
Posts: 55
Joined: Fri Sep 28, 2018 12:19 am

### Calculating k

I understand how to find m and n using concentrations of different initial rates but then how do you find k? Do you just plug in a random rate with its corresponding concentrations?

caseygilles 1E
Posts: 73
Joined: Fri Sep 28, 2018 12:18 am

### Re: Calculating k

Yes, if you are given initial concentrations for every substance in the rate law and you are given the rate, we can use simple math to find k.
Example: for A+B---> products, rate=1.5 * 10^-7 mol/L*s and [A]=2.0 * 10^-2 mol/L , [B]=3.7 * 10^-2 mol/L:
rate=k[A][B] ------- k=rate/[A][B]-------- k= (1.5 * 10^-7 mol/L*s )/((2.0 * 10^-2 mol/L) * (3.7 * 10^-2 mol/L)) = 2.03 * 10^-4

Posts: 60
Joined: Fri Sep 28, 2018 12:27 am

### Re: Calculating k

Since you know concentrations, unique rate (from table), m and n (from prior calculations), you only have one unknown variable (k). Therefore, by plugging in all these values, you'll be able to get k.

Brian Chang 2H
Posts: 65
Joined: Fri Sep 28, 2018 12:17 am

### Re: Calculating k

If you have m and n you can plug them in to find K,

similarly, you can use k to derive either m or n.

You CANNOT solve for more than 1 unknown though.