Reactants that don't play a part in the reaction

Arrhenius Equation:

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Glenda Marshall DIS 3M
Posts: 68
Joined: Sat Sep 27, 2014 3:00 am

Reactants that don't play a part in the reaction

Postby Glenda Marshall DIS 3M » Tue Feb 24, 2015 10:19 pm

In question #14.85 part (b), it asks to write the overall react with the rate law

rate=k[I]^2[Ar] (products are I2 and Ar; the role of Ar is to remove energy as the product forms).

The reaction they gave was 2I ----> I2

How do we know to exclude the Ar and why would it be a termolecular elementary reaction if the Ar is excluded?

Neil DSilva 1L
Posts: 70
Joined: Fri Sep 26, 2014 2:02 pm

Re: Reactants that don't play a part in the reaction

Postby Neil DSilva 1L » Wed Feb 25, 2015 12:25 am

I think we exclude the Ar because it occurs as a reactant and a product, so it would just cancel out.

Molecularity is determined by the number of reactants that take part in an elementary reaction, so even though the Ar is canceled out, it is still used up in the elementary step, so it contributes to the molecularity of the equation.

Glenda Marshall DIS 3M
Posts: 68
Joined: Sat Sep 27, 2014 3:00 am

Re: Reactants that don't play a part in the reaction

Postby Glenda Marshall DIS 3M » Thu Feb 26, 2015 11:35 am

Thank you so much!


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