Units of rate

The vast majority of the kinetic detail is presented in tabular form. Amassing of data in this way has revealed a number of errors, to which attention is drawn, and also demonstrated the need for the expression of the rate data in common units. Accordingly, all units of rate coefficients in this section have been converted to mole.l-1.sec-1 for zeroth-order coefficients (k0), sec-1 for first-order coefficients (kt), l.mole-1.sec-1 for second-order coefficients (k2), l2.mole-2.sec-1 for third-order coefficients (fc3), etc., and consequently no further reference to units is made. Likewise, energies and enthalpies of activation are all in kcal. mole-1, and entropies of activation are in cal.deg-1mole-1. Where these latter parameters have been obtained over a temperature range which precludes the accuracy favoured by the authors, attention has been drawn to this and also to a few papers, mainly early ones, in which the units of the rate coefficients (and even the reaction orders) cannot be ascertained. In cases where a number of measurements have been made under the same conditions by the same workers, the average values of the observed rate coefficients are quoted. In many reactions much of the kinetic data has been obtained under competitive conditions such that rate coefficients are not available in these cases the relative reactivities (usually relative to benzene) are quoted. 

By custom, the units of concentration are always included in the units of rate constants but are customarily omitted for equilibrium constants. Problem 7-15 provides further insights. 

The units of rate constant for a first order reaction from equation (1.21) is measured as (time)-1 and can be represented as sec-1, min-1 or hour-1. 

Units of rate constant is (cone.) 2 (time)1 or generally mol-2 lit2sec 1 or mol2 dm6 sec-1. 

The decay constant A. represents the average probability per nucleus of decay occurring per unit time. Therefore, we are taking the probability of decay per nucleus, and multiplying it by the number of nuclei present so as to get the rate of particle emission. The units of rate are (disintegration of nuclei/time) making the units of the decay constant (1/time), that is, probability/time of decay. 

A cooling tower has been designed to handle 7650 gpm of hot water at a 15°F range and a 10°F approach to 70°F wet-bulb temperature. Determine the tower units of rated area. 

Because the general form of the units of rate constants is (time) (concentration)1 , the unit of the rate constant of a zero-order reaction is (time) 1(con-centration)1. The rate of zero-order reaction is independent of the concentration of the reactant, which is often encountered in heterogeneous reactions on the surface such as activated carbon adsorption. 

PLl-r(Pu) = load loss density under rated conditions (per unit of rated load PR loss density. 

The units of rate are given in terms of concentration per unit time or pressure per unit time, i.e. 

Overall reaction order Units of rate constant k Method to determine /cfor rate laws with one reactant... 

Rate constant is a measure of the intrinsic rate of a reaction. The unit of rate constant is sec-1. 

The units of rate constant for a given reaction can be determined by starting with the appropriate rate equation for the reaction, as is shown in the following examples. 

The units reported here differ from those used in the oxidation of carbon monoxide in that bar is used in place of atmosphere for pressure measurements and tau was defined in terms of grams of catalyst divided by the molar flow rate of die feed, resulting in the units of rate being (mol g.cat 1 s 1 ). 

Order Rate equation Differentiai form Integrated form Units of rate constant Half-life... 

Example 2. If the conditions are changed to 110/85/70, the corresponding rating factor is 1.422. This represents a greater degree of difficulty, so 10,000 (1.422) = 14,220 tower units of rated area. 

Figure 9.8. Compensation plot for ethyne hydrogenation on nickel-copper powders (A in units of rate of pressure fall...

Overall reaction Units of rate constant Method to determine /r for rate... 

Boiler Horsepower - A unit of rate of water evaporation equal to the evaporation per hour of 34.5 pounds of water at a temperature of 212 degrees Fahrenheit into steam at 212 degrees F. 

Horsepower (Hp) - A unit of rate of operation. Electrical Hp a measure of time rate of mechanical energy output usually applied to electric motors as the maximum output 1 electrical Hp is equal to 0.746 kilowatts or 2,545 Btu per hour. Shaft Hp a measure of the actual mechanical energy per unit time delivered to a turning shaft 1 shaft Hp is equal to 1 electrical Hp or 550 foot pounds per second. Boiler Hp a measure to the maximum rate to heat output of a steam generator 1 boiler Hp is equal to 33,480 Btu per hour steam output. 

Table 4.1 Units of rates/rate constants (for a first-order reaction) for different classes of reactions...

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