Rate Law: Rate Equation For A Chemical Interaction

1328 Words3 Pages

The rate law or rate equation for a chemical reaction is an equation that links the reaction rate with concentrations or pressures of reactants and constant parameters (normally rate coefficients and partial reaction orders).[1] For many reactions the rate is given by a power law such as where [A] and [B] express the concentration of the species A and B, respectively (usually in moles per liter (molarity, M)). The exponents x and y are the partial reaction orders and must be determined experimentally………….(1) According to the law of mass action, the rate of a chemical reaction at a constant temperature depends only on the concentrations of the substances that influence the rate. The substances that influence the rate of reaction are usually …show more content…

For the general reaction aA+bB→cC+dD the rate is proportional to [A]m[B]n; that is, rate=k[A]m[B]n This expression is the rate law for the general reaction above, where k is the rate constant. Multiplying the units of k by the concentration factors raised to the appropriate powers give the rate in units of concentration/time. The dependence of the rate of reaction on the reactant concentrations can often be expressed as a direct proportionality, in which the concentrations may be raised to be the zeroth, first, or second power. The exponent is known as the order of the reaction with respect to that substance. In the reaction above, the overall order of reaction is given by the following: order=m+n The order of the chemical equation can only be determined experimentally, i.e., m and n cannot be determined from a balanced chemical equation alone. The overall order of a reaction is the sum of the orders with respect to the sum of the …show more content…

That reaction is followed by the decomposition of ES to regenerate the free enzyme, E, and the new product, P. For more general information about enzyme-catalyzed reactions, please refer to GENERAL PRINCIPLES [of Enzymes]. To begin our discussion of enzyme kinetics, let's define the number of moles of product (P) formed per time as V. The variable, V, is also referred to as the rate of catalysis of an enzyme. For different enzymes, V varies with the concentration of the substrate, S. At low S, V is linearly proportional to S, but when S is high relative to the amount of total enzyme, V is independent of S. Concentrations is important in determining the initial rate of an enzyme-catalyzed reaction. A more thorough explanation of enzyme rates can be found here: Definition of Reaction Rate. To understand Michaelis-Menten Kinetics, we will use the general enzyme reaction scheme shown below, which includes the back reactions in addition the the forward reactions: E+S−→k1[ES]−→K2E+P E+S←−k3[ES]←−K4E+P…………… (3) Table 1: Model

Open Document