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### 15.19

Posted: **Thu Mar 01, 2018 8:06 pm**

by **sofiakavanaugh**

For this problem, there is a big table full of experimental values and you are asked for the rate law. I was confused on how to calculate the order of B, sorry I cant type the table but if someone could explain to me how they did it that would be amazing.

Thanks

### Re: 15.19

Posted: **Thu Mar 01, 2018 8:44 pm**

by **Sammy Thatipelli 1B**

to calculate the order of b, use experiments 2 and 3. increasing the concentration of B by the ratio 3.02/1.25 increases the rates by (3.02/1.25)^2, and this makes B second order.

### Re: 15.19 [ENDORSED]

Posted: **Thu Mar 01, 2018 8:57 pm**

by **Andrew Nguyen 2I**

Sometimes the order number can be seen by simple observation, though it's better to have a foolproof method for rates like this. The rate changes by a ratio of 50.8/8.7 and the concentration by 3.02/1.25

So, simply equate the concentration raised by the order number equal to rate

(3.02/1.25)^x = 50.8/8.7

where x is the order number; you get 2.416^x = 5.84

take the log of both sides, allowing you to take x down by the log power rule:

x*log2.416 = log 5.84

simplify

x = log2.416/log5.84

You get something very close to 2 such as 1.99, giving you a second order power.