Run 1 9. Fill a cuvette ¾ full with 0.300 M NaOH. 10. Add one small drop of phenolphthalein solution and invert to mix. 11. Place the cuvette in the spectrophotometer. The absorbance reading will appear. Note: Do NOT tap Collect collection device. We are only using the LabQuest to measure the absorbance, not as a data 12. Wait to start recording the time and absorbance in your lab notebook and the report sheet until the reading is between 1.0 and 0.4. If the initial absorbance is below 0.4, remove the cuvette, add a small drop of phenolphthalein solution, invert to mix, and place the cuvette back into the spectrophotometer. Begin timing when you record your first absorbance reading; this is time zero. All other times are recorded relative to time zero. Note: Your instructor may give you alternate directions regarding when to begin recording your data. 13. Record the absorbance every 30. seconds after your initial reading for a total of 180. seconds. 14. When done with the run, remove the cuvette and rinse it with DI water. Lab 14 Kinetics of the Reaction of Phenolphthalein with NaOH Run 2 15. Pipet 20.0 mL of 0.300 M NaOH solution into a small beaker and pipet 10.0 mL of 0.300 M NaCl into it. Mix the solution well. 16. Repeat Steps 9–14 using the resulting solution from Step 15 in place of the 0.300 M NAOH solution and recording the absorbance every 60. seconds for a total of 360. seconds. Run 3 Note: Reaction rates are a function of temperature. It is important that the solutions do not change temperature during the course of the reaction. The cuvettes containing the two lower concentrations of hydroxide ion (Runs 3 and 4) should be removed from the spectrophotometer's light path between readings to prevent the solutions from warming. 17. Pipet 10.0 mL of the solution created for Run 2 into a small beaker and pipet 10.0 mL of 0.300 M NaCl into it. Mix the solution well. 18. Repeat Steps 9–14 using the resulting solution from Step 17 in place of the 0.300 M NAOH solution and recording the absorbance every 120. seconds for a total of 720. seconds. Run 4 19. Pipet 10.0 mL of the solution created for Run 3 into a small beaker and pipet 10.0 mL of 0.300 M NaCl into it. Mix the solution well. 20. Repeat Steps 9–14 using the resulting solution from Step 19 in place of the 0.300 M NaOH solution and recording the absorbance every 120. seconds for a total of 720. seconds.