The rate of the reaction: 2NO + O2 -> 2NO2 is doubled when the concentration of `O_2` is doubled, but increases by a factor of 8 when the concentration of both the reactants is doubled....

The rate of the reaction: 2NO + O2 -> 2NO2 is doubled when the concentration of `O_2` is doubled, but increases by a factor of 8 when the concentration of both the reactants is doubled. Determine the:

a) Order of reaction with respect to NO and O2 (6 marks)

and (b) Overall order of reaction (2 marks)

Expert Answers
gsenviro eNotes educator| Certified Educator

For the given chemical reaction: `2 NO + O_2 -> 2 NO_2`

The rate of reaction is given as the product of concentrations of the reactants, raised to the power by their respective coefficients. Thus the rate of this reaction is given as:

Rate of reaction = `k[NO]^2[O_2]`

where the order of reaction with respect to NO is 2 (exponent to the concentration terms of NO) and with respect to oxygen is 1. And the overall order of reaction is 2 + 1 = 3.

Let us verify this result. If we increase the concentration of oxygen by a factor of 2, using the equation, we can see that the rate of reaction will also increase by 2, since the exponent of oxygen concentration is only 1. In comparison, if we double of concentration of both NO and oxygen, the overall rate of equation is be (2)^2 x (2) = 4 x 2 = 8 times the original rate. These results are in accordance with the given information.

Thus, the overall order of reaction is 3, consisting of order of reaction 1 with respect to oxygen and 2 with respect to NO.

 

Hope this helps.

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