pH (Activity)

Titration of Antacid


  • What pH do you predict an antacid to be?
  • Do you expect the antacid to be a strong acid, weak acid, strong base or weak base?
  • Does brand of antacid matter in the effectiveness?


  1. Retrieve an antacid tablet from the instructor
  2. Crush the antacid in 100 ml of distilled water
  3. Transfer 50 ml of the solution to clean 250 ml beaker
    • Share remaining 50 ml with another group (ensure it is a different tablet)
    • if available, add 5 drops of bromocresol purple (0.04% solution) to each sample
  4. Measure the pH of the antacid solutions and observe color (if using bromocresol purple)
  5. Determine if you want to titrate with an acid or with a base
  6. Titrate each antacid solution with either 0.1N HCl or 0.1N NaOH in 2ml increments (you must decide)
    • if using bromocresol purple, stop when yellow is reached