Purpose: To calculate the concentration, pH of the lactic acid in a Ring Pop.
- Lactic Acid (Ring Pop)
- Base: 0.10M NaOH
- Indicator: Phenolphtalein (ptph)
- Water (50.0mL)
- Electronic Scale
- Stir Stick
- Mortar and Pestle
- 10mL Graduated Cylinder
- 3x 100mL Beakers
- 250mL Beaker
STEP 1: Crush Lactic Acid (Ring Pop) using Mortar and Pestle until it is powder or at least into tiny crystals
STEP 2: Place the crushed Lactic Acid on the electronic scale until you have exactly 10g
STEP 3: Place the 10g of crushed Lactic Acid into a beaker then add 50mL of water into said beaker. Stir the solution until all the Lactic Acid dissolves.
STEP 4: Grab 3 100mL beakers and add 3 drops of ptph in each beaker. Measure out 10mL of the Lactic Acid solution with a pipette and add it into each of the 3 beakers which contain the ptph.
STEP 5: Grab one of the 100mL beaker containing the Lactic Acid solution and the ptph and place it under a burette. Fill the burette with NaOH and titrate the solution until it changes color (you may have to shake the beaker a bit for the change to occur). When it changes color, note how much NaOH was used. Repeat process with the 2 other 100mL beaker.
STEP 6: Once you have titrated your 3 100mL beakers, clean up your station and continue with finding the rest of your data based on what you have achieved from this lab
Results & Calculations
The actual of pH for lactic acid is 2.4. After completing the lab and doing all our calculations, we calculated a pH of 2.5 instead. It is only off by 0.1 so we weren’t off by much. Some possible errors for this cause could be some miscalculations with our data; not all of our Ring Pop dissolved and/or we may not have titrated the acid enough. Maybe if we added a little more of the [NaOH] into the acid, we may have gotten an exact pH.