Question

Draw and label a schematic of an Ag/AgCl reference electrode. As part of your answer, include the ½ reaction that is utilized by this electrode and include a description of how reference electrodes are utilized in electrochemicalmeasurements

Answer 1

It can be easily understood by the following problem

What are the anodic, cathodic, and overall reactions responsible for the potential of the electrochemical cell in Figure 11.8? Write the shorthand notation for the electrochemical cell.

Solution

The oxidation of Ag to Ag+ occurs at the anode, which is the left half-cell. Because the solution contains a source of Cl–, the anodic reaction is

Ag(s) + Cl−(aq)ƒ ⇋ AgCl(s) +e−

The cathodic reaction, which is the right half-cell, is the reduction of Fe3+ to Fe2+.

Fe3+(aq) + e− ⇋ ƒFe2+(aq)

The overall cell reaction, therefore, is

Ag(s) + Fe3+(aq) + Cl−(aq) ⇋ ƒAgCl(s) + Fe2+(aq)

The electrochemical cell’s shorthand notation is

Ag(s) | HCl(aq, aCl− = 0.100), AgCl(sat'd) || FeCl2(aq,aFe2+ = 0.0100), FeCl3(aq, aFe3+ = 0.0500) | Pt(s)

Note that the Pt cathode is an inert electrode that carries electrons to the reduction half-reaction. The electrode itself does not undergo reduction.