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in Chemical Kinetics by (47.5k points)
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How would you calculate the order of the reaction 2NO + O2(g) → 2NO2(g) by an experiment?

Or

prove that 2NO + O2 → 2NO2 is a third order reaction

1 Answer

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by (34.6k points)
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Best answer

2NO(g) + O2(g) → 2NO2(g) 

Series of experiments are conducted by keeping the concentration of one of the reactants as constant and changing the concentration of the others.

Rate = k [NO]m [O2]n

For experiment 1, the rate law is

Rate1 = k [NO]m[O2]n 

19.26 x 10-2 = k [1.3]m [1.1]n ……….(1)

For experiment 2

Rate2 = k [NO]m [O2]n 

38.40 x 10-2 = k [1.3]m[2.2]n …….(2)

For experiment 3

Rate3 = k [NO]m [O2]n

76.8 x 10-2 = k [2.6]m[1.1]n ……(3)

Therefore the reaction is first order with respect to O2

Therefore the reaction is second order with respect to NO 

The rate law is Rate = k [NO]2[O2]1 

The overall order of the reaction = 2 + 1 = 3 

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