## Homework Problem 15.19

$\frac{d[R]}{dt}=-k[R]^{2}; \frac{1}{[R]}=kt + \frac{1}{[R]_{0}}; t_{\frac{1}{2}}=\frac{1}{k[R]_{0}}$

Jazmin_Morales_3J
Posts: 17
Joined: Wed Sep 21, 2016 2:59 pm

### Homework Problem 15.19

Hi guys,

I was doing question 15.19 and I was having trouble finding the order of the reaction of B. According to the solutions manual, the reaction is second order in B, but I don't understand what steps they took to get that answer so any clarification would be much appreciated. Thanks!
Last edited by Jazmin_Morales_3J on Sat Mar 18, 2017 10:40 pm, edited 1 time in total.

Vivian Wang 3J
Posts: 29
Joined: Wed Sep 21, 2016 2:57 pm
Been upvoted: 1 time

### Re: Homework Problem 15.19

Increasing the concentration of B by the ratio $\frac{3.02}{1.25}$ (from experiments 2 and 3) increases the rate by $\left ( \frac{3.02}{1.25} \right )^{2}$.

Therefore, the reaction is second order in B.

Angela_Kim_1N
Posts: 21
Joined: Fri Jul 22, 2016 3:00 am

### Re: Homework Problem 15.19

I am also not understanding this part of the problem. The solution manual states that the rate is increased by (3.02/1.25)^2 however I am not seeing how the rate is increased by this amount.

Thank you!

megan_thi_2j
Posts: 10
Joined: Wed Sep 21, 2016 2:55 pm

### Re: Homework Problem 15.19

I believe that for problems where you can't easily recognize if the concentration is being doubled, etc. then you just use this ratio method. In this problem, the solution manual is observing experiments 2 and 3 that has concentrations, 1.25 and 3.02 respectively. It's really hard to tell what exactly happens from 1.25 to 3.02 to using the ratio of 3.02/1.25 is the easiest!