Order of Reactants

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Lusin_Yengibaryan_3B
Posts: 113
Joined: Wed Sep 30, 2020 9:33 pm

Order of Reactants

Postby Lusin_Yengibaryan_3B » Sat Mar 13, 2021 9:03 pm

I'm still confused about how to identify the order of a reactant. For example, how do we identify the order of reactants, A, B, and C in the following reaction?
2A(g)+2B(g)+C(g)⟶3G(g)+4F(g)

Edward Tang 1k
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Re: Order of Reactants

Postby Edward Tang 1k » Sat Mar 13, 2021 9:08 pm

If this is an elementary step, then the order of the reaction is determined by molecularity and would be second order with respect to A and B and first order with respect to C.

But I think the order of a non-elementary reaction has to be experimentally determined, meaning only with a data table and finding out how the rate of the overall reaction changes with the concentration of specific reactants can we determine the order of each reactant and the overall reaction.

YuditGaribay3J
Posts: 50
Joined: Wed Feb 26, 2020 12:18 am

Re: Order of Reactants

Postby YuditGaribay3J » Sun Mar 14, 2021 3:31 am

Are you missing some information. Usually, you can only use the data table to see how the concentrations and the rate of the species are "changing" over time?

Rachael Cohen 3G
Posts: 53
Joined: Sun Dec 13, 2020 12:17 am

Re: Order of Reactants

Postby Rachael Cohen 3G » Sun Mar 14, 2021 8:47 am

If this is from Sapling question 7, then you have to use the data provided to find the orders. You can write out the rate law (leaving the exponents as variables) for two different experiments and divide them to solve for those variables.

Karina Grover 1A
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Re: Order of Reactants

Postby Karina Grover 1A » Sun Mar 14, 2021 12:02 pm

If you are given elementary steps, then the orders are determined by the coefficients. However, if you are not given elementary steps, then you need to find the experimentally determined rate law from a table of values. This table of values includes concentrations of reactants and the specific rate at those concentrations. Using these numbers, you can determine the order of each reactant and, eventually, the rate constant.

Eve Gross-Sable 1B
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Re: Order of Reactants

Postby Eve Gross-Sable 1B » Sun Mar 14, 2021 12:59 pm

You can't determine the order just by the chemical equation, so that would be an indicator that you'd need more information!

Jaden Joodi 3J
Posts: 104
Joined: Wed Sep 30, 2020 9:31 pm

Re: Order of Reactants

Postby Jaden Joodi 3J » Sun Mar 14, 2021 1:43 pm

Given a formula alone, it is impossible to determine the order of reactants. You must be given a table complete with experiments that allow you to see see what increasing the concentration of only one of reactants does to the amount of product.


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