Syringe titrator stopcock

Unit 7 Lab: Water Hardness CHEM 1806
Purpose: To determine the hardness of your drinking water and the technique of titration

Materials: Student Supplied –distilled water, tap water, books or other height riser

LabPaq materials: 100mL glass beaker, toothpicks, 25 mL Graduated cylinder, test tube clamp holder, 10mL syringe titrator, syringe stopcock, Determination of water harness bag

Procedure:

**You might want to do steps 1-5 one day so the equipment can dry to complete the experiment the next day.

1. Remove the plunger from the syringe titrator and set aside. Attach the stopcock to the end of the titrator and twist into place. This should fit snuggly.

2. Clamp the test tube holder around the middle of the titrator and slide the long end of the holder between two books or risers.

3. Set the 100 mL beaker on a sheet of white paper and adjust the height of the titrator so that the end of the stopcock is within 1cm of the top of the beaker.

4. Place 7-9mL of distilled water in the titrator and practice dispensing 1 drop at a time.

5. When you are comfortable with the technique, dump all of the water in the beaker and titrator down the drain and dry thoroughly.

6. With the stopcock in the closed position, fill the titrator with 9-10mL of the EDTA solution.

7. In a waste glass, drop a few drops of the EDTA solution out of the stopcock to remove any air bubbles.

8. Measure exactly 10mL tap water with the graduated cylinder and place it in the clean, dry beaker. (Bottled water won’t work)

9. Add 5 drops of pH 10 buffer solution to the beaker and carefully swirl the mixture.

10. Dip 1 cm of a toothpick into distilled water and then into the EBT indicator powder. Stir the beaker with the EBT covered end of the toothpick to transfer the EBT to the beaker.

11. Carefully swirl the beaker for 30-60 seconds to dissolve the EBT. The solution should turn a pale pink.

12. Read the initial volume of EDTA and record in the Data Table. (This is Trial 1)

13. Add EDTA solution, one drop at a time, swirling the flask between drops until the beaker solution is a pale blue-gray color for at least 5 seconds.

14. Record the final volume of the EDTA solution remaining in the titrator.

15. Pour the contents of the beaker in the drain; wash the beaker and rinse it with distilled water. Thoroughly dry the beaker.

16. Refill the titrator and read the initial volume of EDTA.

17. Measure 10 mL of tap water and place in the beaker.

18. Follow the steps, as above, to titrate this trial of tap water. (Steps 9-15)

19. Repeat for a 3rd trial.

(2 pts) Data Table: **Remember to record to appropriate sig figs!

Initial EDTA volume

Final EDTA volume

Total Volume EDTA

Trial 1

Trial 2

Trial 3

Average volume

Results and Discussion:

(6pts) Calculate the total water hardness of your water in Molarity and ppm. Show your work.

(3 pts) How much calcium would you ingest if you drink 8-8oz glasses of you water?

(4 pts) Insert a picture of your titration set up.

When you have finished, please save the file as LASTNAME_Water and upload to the Unit 7 Lab dropbox.