AP Chemistry Lab Handout 13 "Weak Acid Titration"

Your Name: ___________________________________

Lab Partners: ____________________________

Purpose: To determine the Molarity of an unknown acid solution using

         a base.

Materials: goggles                      balance

NaOH distilled water scoopula

buret 100.0 mL volumetric flask 125mL Erlenmeyer flask

ring stand buret clamp phenolphthalein

soda 25 mL graduated cylinder pipet

Procedure:

1. Obtain goggles and wear them for the entire lab!

2. Calculate the mass of NaOH needed to make 100.0 mL of

   0.5000 M NaOH.

3. Obtain your NaOH and make the 0.5000 M NaOH solution using

   distilled water and the 100.0 mL volumetric flask.

4. Add 10 mL of NaOH solution to the buret. Rinse the walls

   thoroughly and discard the rinse solution.

5. Fill the buret and record the volume of the NaOH to the nearest

   0.00 mL.

6. Obtain 25.0 mL of soda and place it into the 100 mL Erlenmeyer

   flask.

7. Add three drops of phenolphthalein.

8. Begin adding NaOH with the stopcock of the buret open fully.

9. Slow down the addition of NaOH when the pink color does not

   disappear as quickly.

10. Slow down the addition of NaOH to a drop at a time, swirling

    the flask gently, until the solution remains a light pink color.

11. Record the volume of the NaOH and determine the amount of NaOH

    used to neutralize the acid in the soda.

12. Empty the flask, rinse and repeat steps 5 – 11 twice more.

13. Calculate the Molarity of the acid in the soda for each trial.

14. Average the Molarity of the acid for all three trials.

Observations:

Data:

	Trial 1	Trial 2	Trial 3
Initial volume of NaOH
Final volume of NaOH
Volume of NaOH used

Calculations:

Error Analysis:

Conclusion: _______________________________________________________

_________________________________________________________________

_________________________________________________________________

Be sure to include the balanced chemical reaction for this lab in

your conclusion.