Potentiometry.

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Presentation transcript:

potentiometry

In analysis we have electrochemical method Physicochemical method that measure certain electron property of substances which is proportional to its concentration Ex. Potentiometry Polarography Electrophoresis Conductometry

Potentiometric titration * It measure the charge of potential. * Is made by titration. Used for *acid-base ,redox , complex ,precipitation titration. *Very dilute solution. *Colored and turbid solution. *In case of no suitable indicator is available.

instrument referance electrode: Ag/Agcl pH meter : * indicator electrode. * Potentiometer meter. * magnet. referance electrode: Is electrode with a constant potential . Ex. normal electrode.(SHE) calomel electrode. To make a potentiometric determination of an analyte in a solution, the potential of the cell is measured. This measurement must be corrected for the reference and junction potentials ,A pH meter is an electronic instrument used to measure the pH (acidity or alkalinity) Ag/Agcl

:Indicator electrode The potential of this electrode will change due to any change in potential of solution as a result of change in concentration of substance. Ex. * ion selected electrode. glass electrode A glass electrode is a type of ion-selective electrode made of a doped glass membrane that is sensitive to a specific ion. It is important part of the instrumentation for chemical analysis and physico-chemical studies.

Glass combined electrode reference electrode internal reference electrode Ag/Agcl salt bridge PH sensitive glass ( full of buffer )

objectives Titration of a weak acid ( acetic acid ) against a strong base ( NaOH)

Potentiometric titration curve of 0.1 n NaOH against ? N acetic acid pH PH at alkaline solution PH at e.p *NaOH curve more sharp than NH4OH PH at acidic solution mls at e.p mls