pH curves

• Calibrating the pH meter

  1. Rinse the pH probe thoroughly with distilled water and shake it to remove excess water
  2. Place probe in a pH 4.00 buffer solution and record pH reading
  3. Rinse pH probe with distilled water and repeat step 2 but with 7.00 and 9.00 pH buffer solutions
  4. Then plot a graph using recorded pH reading against pH of buffer solution
  5. That's the calibration curve
• Why is calibrating a pH meter just before using, improves accuracy of the pH measurement?

  Over time, the meter does not give accurate results
• Measurement of pH of a mixture of weak acid and a strong base

  1. Rinse burette with the weak acid and fill it with the weak acid
  2. Use burette to transfer 20 cm^3 of the acid into a beaker
  3. Fill a new clean burette with strong base
  4. Rinse pH probe with distilled water and place it in the weak acid beaker and record the pH reading
  5. Using second burette, add 2 cm^3of the strong base into the beaker and record pH reading
  6. Repeat step 5 until 40 cm^3 of strong base is used
  7. Use calibration graph to appropriate the pH readings