Order of Reaction

(redirected from Reaction order)

Order of Reaction


a concept in chemical kinetics. The order of a reaction is determined as the sum of the exponents n1 and n2 in the equation

r = k [A1]n1[A2]n3

which expresses the dependence of the reaction rate r on the concentrations [A1] and [A2] of the initial materials, where k is the rate constant. Reactions in which n1 + n2 = 1, 2, … are called first-order reactions, second-order reactions, and so on. The individual exponent in equation (1) is called the order of the reaction for the corresponding substance.

In simple reactions the rate in one direction, according to the mass action law, is subject to equation (1), and n1 and n2 coincide with the number of molecules of substances A1 and A2 that take part in the elementary stage of the reaction. The rates of complex reactions are sometimes also expressed by equations of type (1); at the same time, however, the order of a reaction may be different from the stoichiometric coefficient of the substance in the reaction equation (written with the smallest integral stoichiometric coefficients), and it may be a fraction. Fractional and zero orders, as well as integral orders, are common for heterogenous catalytic reactions; negative orders are also known.


References in periodicals archive ?
2] are the apparent rate constants, m and n are the kinetic exponents of the reaction, and m + n gives the overall reaction order.
It enables the calculation of additional parameters such as reaction order, reaction rate constant and activation energy.
Owing to the positive reaction order of the hypophosphite concentration ([beta] = 0.
The integral method that was commonly selected for the reactions of known reaction order with respect to reactants was used to determine the rate parameters.
2]S oxidation with activated carbon catalysts Investigators Catalyst Reaction order with respect to [O.
The reaction order n of neat nylon-6 and the blends with low PEO content were approximated to 1, indicating of the one-step reaction, while the reaction process of the blends with high PEO content was deviated from one-step reaction.
Reaction model Reaction mechanism A Jander's equation Spherical symmetry three dimensional diffusion B Zhuravlev-Lesokhin-Tempelman Three dimensional (ZLT) equation diffusion C Maple's equation One step random (first-order) nucleation and growth D Avrami-Erofeev Random nucleation equation and growth n = 3 / 2 E Avrami-Erofeev Random nucleation and equation growth n = 2 F Avrami-Erofeev Random nucleation and equation growth n = 3 G Avrami-Erofeev Random nucleation and equation growth n = 4 H Reaction order Chemical reaction n = 1 I Reaction order Chemical reaction n = 3 / 2 No.
a]), heat of reaction ([DELTA]H), pre-exponential factor (Z), reaction order (n) and rate constant (k).
3]m), n is the reaction order which is 1 in this case, [k.