Wai Long Lam
Experiment 9: Rate Law Determination of the Crystal Violet Reaction Goals: Under stand 1st, 2nd , and 3rd order chemical reactions, learn graphing options available on LogerPro Purpose: Determine the reaction order with respect to crystal violet for the reaction between crystal violet and sodium hydroxide. Introduction: The rate expression for this reaction is of the form: rate = K(CV+)M(OH-)N Where k = re constant, m is the order of the reaction with respect to the concentration of CV+, and n is the order of the reaction with respect of OH-. In the experiment the concentration of OH- is purposely made 1000 times larger then Concentration of CV+. Thus, the concentration of OH- changes so little during the reaction that can be assumed to be constant. Materials: IBM Compatible computer, serial box interface, LoggerPro Software, Vernier colorimeter, plastic cuvette, 250-mL beaker, 0.020M NaOH, 2 x 10-5 M crystal violet, distilled water, stirring rod, two 10-mL graduated cylinders. Procedure:
1. Obtain and wear safety glasses.
2. Measure out 10 mL of 0.020M NaOH using a 10 mL graduated cylinder. Use another 10 mL graduated cylinder and measure out 10 mL of 2.0 x 10-4 c crystal violet solution. 3. Preapre the computer for data collection by opening “Exp 30” from the Chemistry with Computers experiment files of LoggerPro. The vertical axis has absorbance scaled from 0 to 0.35. The horizontal axis has scaled from 0 to 20 minutes. 4. Calibrate the colorimeter for 0% transmittance (no light) and 100% transmittance (maximum light). a) Fill a cuvette ¾ full of distilled water. This is called the blank since it absorbs no visible light and allows 100% transmittance. The outside of the cuvette should be clean and dry. Only touch the cuvette on the ribbed sides. Position the cuvette with the reference mark facing toward the white reference mark at the right cuvette slot of the colorimeter. b) Choose calibrate from the experiment...
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