Powers of Concentrations in Rate Law`

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Merzia Subhan 1L
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Joined: Thu Jul 13, 2017 3:00 am

Powers of Concentrations in Rate Law`

Postby Merzia Subhan 1L » Wed Mar 14, 2018 9:57 pm

Since when writing rate laws, the coefficients of the equation are not the power in the rate law, like 3 I- is not [I-]^3, how would you determine the power of a concentration in a rate law? Is it impossible to determine just by looking at the chemical equation?

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Joined: Fri Sep 29, 2017 7:04 am

Re: Powers of Concentrations in Rate Law`

Postby DianaTrujillo2K » Wed Mar 14, 2018 10:02 pm

The order of a rate law is determined experimentally using the method of initial rates or by looking at the graphs. When the observed rate law is given along with the elementary steps of a reaction, you can use the pre-equilibrium approach to determine the slow step that determines the rate of the overall reaction. In the pre-equilibrium approach the coefficients of the reactants are the powers of their concentrations.

Angel R Morales Dis1G
Posts: 50
Joined: Sat Jul 22, 2017 3:01 am

Re: Powers of Concentrations in Rate Law`

Postby Angel R Morales Dis1G » Wed Mar 14, 2018 11:01 pm

You can write the rate law from the the formula itself, A+B -> C, r=k[A][B], but you wouldnt know what order it is until you find the exponents to each reactant, most likely from a data table.

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