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 ?
where t stands for time, k for the reaction rate constant, and n is the reaction order with respect to [H.
where m is the mass, subscripts o indicate the initial time at 300 [degrees]C, subscript t represents any time during run, f denotes the final pyrolysis temperature, n is the reaction order and can take values 0.
The order of the isomerisation reaction is in contrast to the reaction order for the isomerisation reaction of 9c12c fatty acids in edible oils reported by Leon-Camacho et al.
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 activation energy for dehydroxilation was evaluated by Freeman-Carroll method which enables, from the exploitation of one DTG peak, to determine besides activation energy of reaction also the reaction order and the rate constant (Freeman and Caroll, 1958).
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.