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Chemistry · Ch 6 — Chemical Kinetics

Order and molecularity of elementary reactions

6.4.3

Order and molecularity of elementary reactions

The rate law for the elementary reaction

2NO2(g)⟶2NO(g)+O2(g)\mathrm{2NO_2(g) \longrightarrow 2NO(g) + O_2(g)}

is found to be rate =k[NO2]2= k\mathrm{[NO_2]^2}. The reaction is second order and bimolecular: the order of the reaction is 2 and its molecularity is also 2.

Note

The book prints this equation as "2NO₂(g) ⟶ 2NO₂(g) + O₂(g)" — the product formula repeats the reactant. The correct product, as the book's own section 6.4.2 prints for the same reaction, is 2NO(g); the equation above shows the correct form.

For the elementary reaction

C2H5I(g)⟶C2H4(g)+HI(g)\mathrm{C_2H_5I(g) \longrightarrow C_2H_4(g) + HI(g)}

rate=k [C2H5I]\text{rate} = k\,\mathrm{[C_2H_5I]} …

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