Introductory examples for kinetics

Even more complicated than equilibrium modeling is the modeling of kinetically controlled processes (for theory see chapter 1.2). Normally the reaction rate varies 

For kinetic modeling in PHREEQC two keywords are necessary KINETICS n (n = number of SOLUTION, for which the kinetics shall be calculated) and RATES. For both keywords, a rate name has to be entered, e g. calcite when the dissolution of calcite shall be kinetically modeled. The general syntax within the keyword KINETICS is as shown in Table 25. 

The general syntax for RATES is rate name and -start -end. A BASIC program is obligatory between -start and -end (see chapter 2.2.2.2.1). 

As reaction rates can be fitted mathematically in very different manners, there is an option (and need) in PHREEQC to declare any mathematical term in the form of a little BASIC program within the keyword RATES as will be shown in the following example of a time-dependent calcite dissolution  

130 moles = moles time //this line is a must for each BASIC-program 140 if (moles m) then moles = m 150 if (moles = 0) then goto 200 160 temp = tot( Ca ) 

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