DRAFT: This module has unpublished changes.

Materials and Equipment:

  

- Data collection system                   - Clamp. right-angle

- pH sensor                                      - Funnel

- Drop counter with micro stir bar    - Potassium hydrogen phthalate (KHP), 0.6 g

- Magnetic stirrer                             - Sodium hydroxide (NaOH), 0.40 g

- Ring stand                                     - Buffers, pH 4 and pH 10, 10-mL

- Beaker (2), 100-mL                       - Water, deionized, 250-mL

- Beaker (2), 10-mL                         - Wash bottle with deionized water

- Volumetric flask, 100-mL               - Parafilm or aluminum foil

- Buret, 50-mL                                 - Cotton swab or tissue

- Buret clamp

 

Methods:

 

1. Weigh out 4.2g of NaOH. Dissolve it quickly in about 50-mL water in a 250-mL Erlenmeyer flask.

 

2. Carefully transfer the solution into a 1-L volumetric flask and fill the flask to the 1000-mL mark with deionized water.

 

3. Seal the flask with its stopper, invert the flask, and shake it gently. Then vent the flask.

 

4. Transfer the solution into a 1-L plastic bottle and close it. Label the bottle properly.

 

5. Start a new experiment on the data collection system.

 

6. Connect a pH sensor and the Rotary Motion sensor to data collection system.

 

7. In DataStudio create a calculated dataset for Volume: V= 670* x. (Before exiting the Calculator, click on the Properties button and enter name, unit for the new dataset as Volume, and mL, respectively).

 

8. In DataStudio create a calculated dataset for the first derivative of the pH vs. Volume. Use pH measurements for x. The equation is: dpH= derivative (2,x). (Before exiting the Calculator, click on the properties button and enter name for the new dataset as dpH).

 

9. Display the pH on y-axis and Volume on x-axis.

 

10. Setup the Titrator pump.

 

11. Rinse the syringe on the Titrator pump.

 

12. Setup the Titrator Accessory.

 

13. Calibrate the pH sensor.

 

14. Add the micro stir bar to the end of the pH sensor.

 

15. Setup the titrant container and replace the cap on the bottle, but not airtight.

 

16. Load the syringe on the pump with the titrant solution.

 

17. Prime the pump on the Titrator. 

 

18. Measure about 0.200 g of KHP to the nearest milligram and record this value in Table 1. Then wash the KHP from the weighing dish with about 50 mL of water, into a 180-mL titration jar. (In order to expedite the titration, while a sample is being titrated, prepare two additional samples for titration).

 

19. Add enough deionized water to the solution so the tip of the pH sensor is covered with solution.

 

20. Turn on the magnetic stirrer at a steady rate.

 

21. Display the pH on the y-axis of a graph and Drop Count on the x-axis.

 

22. Start recording data.

 

23. Press the "Run" button on the Titrator to start the titration.

 

24. Continue the titration past the equivalence point until the pH curve flattens.

 

25. Stop recording data.

 

26. Repeat the titration procedure with two more KHP samples. Record the mass of the samples in Table 1.

 

27. Once you determine the concentration of the NaOH solution, label the solution and place it in a safe place for use in the "Acid-Base Titration" activity.

 

28. Save your experiment and clean up according to your teacher's instructions.

 

29. Print the graph.

 

30. Clean the syringe in the Titrator.

 

 

DRAFT: This module has unpublished changes.