Purpose: To find the pH value and concentration of our given acid (citric acid)


  1. Measure 5g of our acid 
  2. Grind up acid with mortar and pestle

3. Dissolve solid in 50ml of water

4. Measure out 10ml of solution and pour into beaker with two drops of phenolphthalein

5. Titrate 0.10M of the base (sodium hydroxide) into 10ml of our acid solution

6. Keep titrating until our solution turns pink

7. Repeat step 6, three times

8. Write down volume used

9. Calculate the concentration of our base, NaOH, which gives the concentration of acid

10.Use the values to calculate the pH of acid


  • 5g of citric acid
  • 50ml of water
  • 50ml of NaOH
  • Pipette
  • 2 beakers
  • 1 flask
  • 2 graduated cylinders


Test Initial Volume Final Volume Total Volume Used
1 0ml 2.8ml 2.8ml
2 2.8ml 5.4ml 2.6ml
3 5.4ml 8.0ml 2.6ml





I learned that the role of phenolphthalein plays an important role in this lab because we wouldn’t be able to calculate the concentration or pH without knowing when the solution turns pink. After our calculations, it made sense that our pH value was in between 1 and 2 because the pH of our base is 13 and together they equal 14.

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