15.15 Rate Law


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Kathleen Vidanes 1E
Posts: 62
Joined: Fri Sep 29, 2017 7:07 am

15.15 Rate Law

Postby Kathleen Vidanes 1E » Tue Feb 27, 2018 7:30 pm

The question reads: In the reaction CH3Br(aq) OH (aq) S CH3OH(aq) Br (aq), when the OH concentration alone was doubled,
the rate doubled; when the CH3Br concentration alone was increased by a factor of 1.2, the rate increased by a factor of 1.2. Write the rate law for the reaction.

I'm still confused as to how the proportionality relates to the rate law (rate = k[CH3Br][OH-]). Can someone please explain this? Thank you.

Sarah Rutzick 1L
Posts: 50
Joined: Tue Oct 10, 2017 7:13 am

Re: 15.15 Rate Law

Postby Sarah Rutzick 1L » Tue Feb 27, 2018 8:34 pm

When the OH- concentration doubles, the rate increased by the same factor, and when the CH3Br concentration increases by a factor or 1.2, the rate increased by the same factor as well. Therefore, both reactants form a 1:1 ratio with the rate law, yielding the rate above. If, for example, when the concentration of OH- doubled and the rate quadrupled, you would know that the rate law is rate = k[CH3Br][OH-]^2.

ClaireHW
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Re: 15.15 Rate Law

Postby ClaireHW » Wed Feb 28, 2018 4:13 pm

For this problem, why aren't the products considered in the rate law?

(Claire Woolson Dis 1K)

Jessica Wakefield 1H
Posts: 58
Joined: Thu Jul 27, 2017 3:00 am

Re: 15.15 Rate Law

Postby Jessica Wakefield 1H » Thu Mar 01, 2018 12:56 pm

if your concentration doubles and your rate doubles as well, the interaction is proportional and thus the order is considered first
in this problem they said that when concentration is increased by 1.2 the rate does as well and also when the other concentration is doubled the rate does as well, demonstrating this proportionality that would classify the reaction as first order

Ishita Monga 1B
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Re: 15.15 Rate Law

Postby Ishita Monga 1B » Thu Mar 01, 2018 3:37 pm

ClaireHW wrote:For this problem, why aren't the products considered in the rate law?

(Claire Woolson Dis 1K)


to make calculations easier we only consider the reactants when determining the rate law.


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