Using the Solver An Example

The following example illustrates the ease with which the Solver can be used to perform non-linear least-squares curve fitting. Here we analyze kinetics data (absorbance vs. time) from a biphasic reaction involving two consecutive first-order reactions (A =— B =— C) to obtain two rate constants and the molar absorptivity of the intermediate species B. 

The equations for the concentrations of the species A, B and C in a reaction sequence of two consecutive first-order reactions can be found in almost any kinetics text. The expression for [B]f is 

A stopped-flow spectrophotometer was used to obtain the kinetics data for the reaction of a nickel(II) complex NiL2 of a substituted bidentate diamine ligand (L = tetmeen = 2,3-dimethyl-2,3-diaminobutane) with cyanide ion. The reaction is biphasic one diamine ligand is replaced by two cyanide ligands, then the second diamine ligand is replaced  

In the expression for [B]t (equation 12-7), [A]o is the initial concentration of the reactant species NiL22+, and k and k2 are the rate constants for reactions in equations 12-7 and 12-8. We use [B]f together with Beer s law to write 

In column E the squares of the residuals are calculated. The sum of squares is obtained in cell E27, using the E tool (select cell E27, click twice on the E tool). 

---