Experiment Notes: Yogurt Titration

Apparatus and Reagents Needed

• 25 mL burette with stand
• White porcelain basin
• Magnetic stirrer
• pH meter
• Weighing balance
• 10 mL measuring cylinder
• Plastic dropper
• 0.1 mol NaOH
• Phenolphthalein

Sample Preparation

1. Weigh out 10 g of yogurt into the porcelain basin.
   • If mass exceeds 0.05 g, remove excess using a small spoon.
   • Note the mass of yogurt used after stabilization.
2. Add 10 mL of water into the basin.
3. Stir the yogurt mixture thoroughly using the magnetic stirrer.
4. Measure the pH of the yogurt after mixing.

Titration Procedure

1. Add 1 mL of phenolphthalein to the yogurt.
2. Note the initial volume of NaOH in the burette.
3. Titrate the yogurt with 0.1 mol NaOH until a faint pink color appears.
   • Note: Yogurt is viscous, hence mixing takes longer.
   • As NaOH is added, viscosity decreases.
4. Once faint pink is observed, wait for 10 seconds to ensure endpoint is reached.
5. Note the volume of NaOH used.
6. Repeat the titration.
   • Results should agree within 0.05 mL.