Presentation on theme: "Determination of the Rate Law for Food Coloring Bleaching"— Presentation transcript:
1Determination of the Rate Law for Food Coloring Bleaching
2Pseudo-Order Kinetics dye + OCl- productsRate = k[dye]a[OCl-]bAnalyzing rate law is difficult when 2 concentrations are varying. So…Force one to be constant
3Pseudo-Order Kinetics dye + OCl- productsRate = k[dye]a[OCl-]bIf [OCl-] is large and [dye] is small then the [OCl-] is smallk’ = kx[OCl-]bRate = k’x[dye]a
4Pseudo-Order Kinetics dye + OCl- productsRate = k’x[dye]aNow the problem is easier. Run the reaction and graphically analyze the data as 0th, 1st, or 2nd order.Now you have the reaction order in dye. The apparent rate constant can be calculated too.
12Procedure Design Considerations How will you determine the volumes of FD&C blue #1 and bleach to use for the reaction to be complete in approximately minutes.A good set of starting concentrations are[dye]o = ~2.5 x 10-6 M [OCl-]o = ~0.02 M(Stocks: [dye] = ~5 x 10-6 M; [OCl-] = 0.67 M )What kind of data will you obtain from the Spectronic-20 spectrophotometer and how will that help you with this determination?How will you set up the Spectronic-20 spectrophotometer?4. What should you use as your blank?
13Procedure Design Considerations How will you manipulate the data to determine the rate law?How will you deal with the 2 variables in the general rate law? Remember: [dye]o must stay constant.How will you determine k?How will you determine the coefficients a, b?Hint: Do you absolutely need to convert absorbance to concentration?Note: Method of initial rates will not work well here