Acid/Base Titration Lab Procedure/Data Table Name

AP Chemistry/Langellier

Procedure: Use the members of your lab group to split up the work, if you want to get done in a timely fashion!

1.  Determine the amount of 19M NaOH solution that is needed to make 250 mL of approximately 0.1M NaOH (This was done as a prelab exercise!). Obtain this volume of the concentrated NaOH and dilute to 250mL in a 500-mL flask by adding 250 mL of deionized (DI) water. Mix well by swirling. 19M NaOH is very concentrated and very caustic. Keep off your skin, clothes, etc. Goggles and apron are a necessity! This becomes your group’s entire supply of NaOH for the lab—Do not waste it, dump it, or randomly add water to this flask!

2.  Obtain a buret and set up a ringstand with a buret clamp. Using the prepared NaOH solution, rinse the buret with 3 small (~5mL) portions of NaOH, running each portion out through the tip of the buret. Carefully fill the buret to just above the 0.00 mL mark. Discharge a ‘blast’ of NaOH into a waste beaker in order to remove any air bubble from the tip of the buret. Record the initial volume of NaOH in your data table.

3.  Determine the mass of KHP needed to react with 25 mL of 0.1M NaOH. (Also done in prelab) Mass out approximately this amount of KHP (±0.1 g), recording the exact mass in your data table. Using approximately 25 mL of deionized water, dissolve the KHP in a 250-mL Erlenmeyer flask. Be patient as there will be some back-up in the line; we only have 2 analytical balances. Be gentle and kind to the balance!

4.  Add 2 drops of phenolphthalein indicator to the flask, and titrate it to a pale pink endpoint. Record the volume of NaOH in your data table. Record value even if you feel you’ve ‘overshot’ the endpoint. Your eye alone cannot determine the goodness of a titration. Record final value and do the math first!

5.  Refill the buret, read and record the new initial volume, and repeat steps 3 and 4 with a second KHP sample.

6.  Each group member a sample of KHP of unknown mass from Mr. Langellier. Record the number of the unknown in your data table. Pick the order in which you’ll do the titration of your unknowns, and take turns titrating your samples, recording data for your own unknown.

7.  All group members should assist each other to get ready for their unknown titration (refill buret with NaOH, obtain needed DI water, etc.). When all members have completed their unknown titration, the group may perform a third standardization titration if desired. Once all titrations are complete, clean up: Excess NaOH can be poured into the NaOH collection beaker, all titrated solutions can be poured into the sink. Use soap/a brush to wash your glassware. The buret can be emptied, rinsed (x2) with tap water, then given a final rinse with DI water. Leave to drain in buret clamp, upside down with stopcock open.

Standardization
Trial 1 / Standardization
Trial 2 / Unknown
Trial
Mass KHP (g) / XXXXXXXXX
Unknown number / XXXXXXXXX / XXXXXXXXX
Volume final (mL)
Volume initial (mL)
Volume NaOH used
Notes: