9 - pH CHANGES

• METHOD?

  1. Rinse pH meter with deionised water
  2. Calibrate using solutions of known pH
  3. Plot calibration curve of recorded pH against pH metre reading
  4. Titrate
  5. Plot graph of pH on y-axis and volume of alkali on x-axis
  6. Draw smooth curve through points, ignore anomalies
• WHAT IS EQUIVALENCE POINT?

  vertical part of graph (neutralisation)
• WHAT IS HALF NEUTRALISATION?

  when pH = pKa
• CAUSES FOR ANOMALY?

  ineffective stirring
• HOW TO MAKE RESULTS MORE RELIABLE?

  pH reading taken more frequently near end-point
• WHAT IS USED TO DELIVER SOLUTIONS IN A TITRATION AND WHY?

  burette as it can deliver variable volumes
• WHY DOES CALIBRATING A pH METER IMPROVE ACCURACY?

  over time meter does not give accurate readings
• ASIDE FROM CALIBRATION HOW ELSE COULD pH READINGS ACCURACY BE IMPROVED?

  water bath to keep solution at a constant temperature as pH changes with temperature