Methods to Determine End Point in Potentiometric Titrations

• Methods to Determine End Point in Potentiometric Titrations, the end point is identified by monitoring changes in the electrode potential as the titrant is added to the analyte solution.
• Several methods can be used to accurately determine the end point:

1. Graphical Methods to Determine End Point in Potentiometric Titrations

• • The electrode potential is plotted against the volume of titrant added, producing a titration curve.
  • The end point corresponds to the inflection point or the point of the steepest slope on the curve, indicating a sudden change in potential that marks the completion of the reaction between the analyte and titrant.

2. First Derivative Method to Determine End Point in Potentiometric Titrations

• • The first derivative of the titration curve (dE/dV) is calculated and plotted against the volume of titrant added.
  • The end point is identified as the maximum peak, which represents the most significant change in potential per unit of titrant added.

3. Second Derivative Method

• • The second derivative of the titration curve (d²E/dV²) is calculated and plotted.
  • The end point is determined where the second derivative crosses zero, signaling a transition from positive to negative (or vice versa). This method is particularly useful when the inflection point is weak or not well-defined.

4. Gran’s Method

• • A plot is made with the volume of titrant added (V) on the x-axis and the product of the volume and potential difference (VE) on the y-axis.
  • The end point is found by extrapolating the linear sections before and after the equivalence point and determining their intersection. This method is useful for titrations with small potential changes or poorly defined inflection points.

5. Equivalence Point Calculation

• • Theoretical equivalence point is calculated based on the stoichiometry of the reaction and the initial analyte concentration.
  • This method provides an approximate guide for the end point, assuming that the reaction between the analyte and titrant follows a complete stoichiometric ratio.

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