15.17

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Abigail Urbina 1K
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15.17

Postby Abigail Urbina 1K » Thu Mar 08, 2018 2:34 pm

When we're solving for the order of a reactant in an equation, we usually go about by finding the experiments in the table in which that reactant's concentration changes and where the other reactants are held constant. However, if one of the reactants is independent of the rate, how does this affect our calculations and how we should go about choosing which experiments to work with? For example, in 15.17a, [C] is independent of the rate. Do we then simply ignore the values listed for [C]0? Meaning, when we solve for the order with respect to A, we look for experiments where [B] is held constant? Similarly, when solving for the order with respect to B, we should look for experiments where [A] is held constant? That's how I went about solving the question. Could someone verify if this is conceptually correct?

Rohan Chaudhari- 1K
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Re: 15.17

Postby Rohan Chaudhari- 1K » Thu Mar 08, 2018 3:54 pm

Yes you are right. Since C is a zero order, its concetration is ignored when determinining the rate of A and B

Dang Lam
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Joined: Thu Jul 27, 2017 2:01 am

Re: 15.17

Postby Dang Lam » Thu Mar 08, 2018 4:08 pm

Abigail Urbina 1K wrote:When we're solving for the order of a reactant in an equation, we usually go about by finding the experiments in the table in which that reactant's concentration changes and where the other reactants are held constant. However, if one of the reactants is independent of the rate, how does this affect our calculations and how we should go about choosing which experiments to work with? For example, in 15.17a, [C] is independent of the rate. Do we then simply ignore the values listed for [C]0? Meaning, when we solve for the order with respect to A, we look for experiments where [B] is held constant? Similarly, when solving for the order with respect to B, we should look for experiments where [A] is held constant? That's how I went about solving the question. Could someone verify if this is conceptually correct?


Yes after you figured out that [C] is 0 order, you "neglect" all the data coming from concentration C because technically, concentration of C has no effect on the rate.

Jennie Fox 1D
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Joined: Sat Jul 22, 2017 2:01 am

Re: 15.17

Postby Jennie Fox 1D » Thu Mar 08, 2018 4:10 pm

Yes, once C is determined to be zero order, you can ignore the concentrations for C entirely, since it does not have an effect on the reaction rate.

veneziaramirez 3I
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Joined: Fri Sep 29, 2017 6:07 am

Re: 15.17

Postby veneziaramirez 3I » Thu Mar 08, 2018 8:21 pm

How can we tell [C] is zero order?

Ammarah 2H
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Joined: Fri Sep 29, 2017 6:06 am

Re: 15.17

Postby Ammarah 2H » Thu Mar 08, 2018 9:47 pm

If you take experiments 1 and 4 to try to solve for the order of C, you'll end up getting (700/400)^n = 1. (n is the order you are solving for). Taking the log of 1 is zero, which is why C has to be zero order!

Merzia Subhan 1L
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Re: 15.17

Postby Merzia Subhan 1L » Thu Mar 08, 2018 11:54 pm

Since [C] is zero order, it is not listed in the rate law. rate=k[A][B]^2


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