Question

Answer All Blanks (Analytical Chemistry):

In potentiometry, the electrochemical cell’s ___________ [(i) potential/voltage, (ii) current or (iii) resistance] between the indicator (or working) and the reference electrode is measured. The analyte concentration/activity is calculated on the basis of______________ equation. A calibration using a series of standard solutions is often used. To minimize the system error, _______ and _________ [(i) temperature,(ii) volume, (iii) moisture, (iv) room light intensity, and/or (v) electrolyte concentration] of the standard and the unknown sample should be kept constant if possible.

Answer 1

In potentiometry, the electrochemical cell’s Potential [(i) potential/voltage, (ii) current or (iii) resistance] between the indicator (or working) and the reference electrode is measured. The analyte concentration/activity is calculated on the basis of Nernst equation. A calibration using a series of standard solutions is often used. To minimize the system error, Temperature and Electrolyte concentration [(i) temperature,(ii) volume, (iii) moisture, (iv) room light intensity, and/or (v) electrolyte concentration] of the standard and the unknown sample should be kept constant if possible.

**For reference purpose:

Nernst Equation:

E = E^o - RT/nF * ln Q

Where E^o is the standard-state reduction potential , R is the gas constant , T is temperature , n is the number of electrons in the redox reaction , F is the faraday's constant, Q is the reaction quotient.

At 25^o C reaction Nernst equation is,

E = E^o - (0.05916/n) * ln Q