AH is the heat of reaction (negative for exothermic reactions), UA is the product of the heat transfer coefficient and area for a coolant jacket, through which flows at high rate a coolant of temperature Tc. [Pg.204]

The remarkable fact about the velocity of reaction was the negative temperature coefficient. The following figures are taken from Bodenstein s paper, and illustrate the way in which the rate of reaction decreases as the temperature rises. [Pg.120]

The temperature domination explains the peninsula in the P-T diagram (Fig. 3.9), and the negative coefficient of reaction rate is due to the shift from point 2 to 3. [Pg.104]

The three compounds exhibit the major superficial features of hydrocarbon combustion the pressure-time curves are sigmoidal, and the rate of reaction, as given by (dAp/dt)max, exhibits a region of negative temperature coefficient. [Pg.103]

By this definition, the specific rate of reaction is uniquely defined, and its sign is always positive. Inversely, the rate of reaction of each component or species participating in the reaction is the specific reaction rate multiplied by the species stoichiometric coefficient with the corrected sign (negative for reactants, positive for products). [Pg.5]

In this expression, we take the negative value of A[X]/ At, when X refers to a reactant to ensure that the rate of reaction is a positive quantity. To obtain a single, positive quantity it is necessary to divide all rates by the appropriate stoichiometric coefficients. If we apply this expression to reaction (20.1), we obtain [Pg.924]

The rate of a process is expressed by the derivative of a concentration (square brackets) with respect to time, d[ ]/dt. If the concentration of a reaction product is used, this quantity is positive if a reactant is used, it is negative and a minus sign must be included. Also, each derivative d[ ]/dt should be divided by the coefficient of that component in the chemical equation which describes the reaction so that a single rate is described, whichever component in the reaction is used to monitor it. A rate law describes the rate of a reaction as the product of a constant k, called the rate constant, and various concentrations, each raised to specific powers. The power of an individual concentration term in a rate law is called the order with respect to that component, and the sum of the exponents of all concentration terms gives the overall order of the reaction. Thus in the rate law Rate = k[X] [Y], the reaction is first order in X, second order in Y, and third order overall. [Pg.280]

Useful reviews of the kinetics of autocatalytic reactions have recently been published by Mata-Perez and Perez-Benito (22) and by Schwartz Q2) For an autocatalytic reaction a plot of r/c, where r is the rate of reaction and c the concentration of reactant, as a function of c should be linear with a negative slope (22). When this analysis is applied to the possibility of autocatalysis of liquids production by LOG, no dependence of r/c on c was found. In fact, least uares "correlation coefficients were in the range 0.01 - 0.03. Although the initid hypothesis of autocatalysis by thiols is shown to be untenable, an alternative is the possibility of autocatalysis by H2S. [Pg.220]

Order of reaction, n (SI unit 1) — If the macroscopic (observed, empirical, or phenomenological) - reaction rate, v, for any reaction can be expressed by an empirical differential rate equation, which contains a factor of the form fc[A] [B]. .. (expressing in full the dependence of the rate of reaction on the concentrations [A], [B]...), where a and /S are constant exponents (independent of concentration and time) and k is the rate constant (rate coefficient) independent of [A] and [B] etc., then the reaction is said to be of order a with respect to A, of order P with respect to B, etc., and of (total or overall) order n = a + p +. .. The exponents a, p, etc. can be positive or negative integral or rational nonintegral numbers. They are the reaction orders with respect to A, B, etc., and are sometimes called partial orders of reaction. Orders of reaction deduced from the dependence of initial rates of reaction on concentration are called orders of reaction with respect to concentration orders of reaction deduced from the dependence of the rate of reaction on time of reaction are called orders of reaction with respect to time . [Pg.468]

Sometimes, but not always, it is possible to define a quantity, known as the rate of reaction, which is independent of the reactants and products. This can only be done if the reaction is of known stoichiometry for some reactions there are numerous minor products and the stoichiometry is uncertain. Another condition for defining a rate of reaction is that the stoichiometric equation must remain the same throughout the course of reaction for some reactions intermediates are formed in significant amounts, and the stoichiometry varies as the reaction proceeds. If these two conditions are satisfied (i.e., if the stoichiometry is known and is time independent), the rate of reaction is given by any of the expressions that appear in Eq. (3). In other words, the rate of reaction is the rate of consumption or formation divided by the appropriate coefficient that appears in the stoichiometric equation. In the case of products these coefficients are called the stoichiometric coefficients in the case of reactants the stoichiometric coefficients are the negatives of the coefficients in the rate equation. As seen in Eq. (3), this division has made the four rates equal to one another, so that the rate of reaction is unique for the reaction under the particular conditions of the experiment. [Pg.197]

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