Reaction rate for specific reactants

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Mara Lockhart 3J
Posts: 53
Joined: Fri Sep 26, 2014 2:02 pm

Reaction rate for specific reactants

Postby Mara Lockhart 3J » Sat Feb 21, 2015 8:23 am

When calculating the order for each reactant, how do you know what experiments to use. For example, in problem 14.15, to find the order for A, when you use experiments 2 and 4, you get 2^a=2, so a=1. However when you use experiments 3 and 4, you get a completely different answer for a, as you get 2^a=8, so a=3.

Niharika Reddy 1D
Posts: 127
Joined: Fri Sep 26, 2014 2:02 pm

Re: Reaction rate for specific reactants

Postby Niharika Reddy 1D » Sat Feb 21, 2015 9:12 am

I'm not sure but I think you are referring to problem 17. When finding order of the reactants from data of experiments with their initial concentrations and initial rates, you should find 2 experiments in which the concentration of one reactant changes but the concentrations of the other reactants stay the same. By using those experiments, you'll get the correct order for the reactant that has a concentration change.

In 4.17, the rate of reaction is independent of [C] since the reaction is zero order in C. Since [C] won't affect the rate, you can ignore [C] when finding 2 experiments to get the order in A and B.

You wouldn't use experiments 3 and 4 to find the order in A because both [A] and [B] are changing. In experiments 1 and 2 or 2 and 4, only [A] is changing so you would be able to find the correct order in A by using either of these 2 sets of experiments. [C] is also changing but we can ignore that since the reaction is zero order in C.

Mara Lockhart 3J
Posts: 53
Joined: Fri Sep 26, 2014 2:02 pm

Re: Reaction rate for specific reactants

Postby Mara Lockhart 3J » Sat Feb 21, 2015 10:22 am

Oh, okay! That makes sense! Thank you!


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