Question

A cell composed of a platinum indicator electrode and a silver-silver chloride reference electrode in a solution containing both and has a cell potential of V. If the silver-silver chloride electrode is replaced with a saturated calomel electrode (SCE), what is the new cell potential?

Answer 1

Explanation:

Let us assume that the solution contains both $Fe^{2+}$ and $Fe^{3+}$ which has a cell voltage of 0.719 V.

Therefore, voltage of cell contains both Ag/AgCl reference electrode where $Fe^{2+}/Fe^{3+}$ electrode is 0.719 V.

As, $E_{cathode} - E_{anode}$ = 0.719 V

It is known that potential of the silver-silver chloride reference electrode is 0.197 V.

Hence, $E_{anode}$ = 0.197 V. Now, calculate $E_{cathode}$ as follows.

           $E_{cathode} - E_{anode}$ = 0.719 V

           $E_{cathode} - 0.197 V$ = 0.719 V

            $E_{cathode}$ = 0.916 V

Now, voltage of the cell that contains both calomel reference electrode and $Fe^{2+}/Fe^{3+}$ electrode as follows.

$E_{anode}$ = calomel electrode = 0.241 V  

           Voltage of cell = $E_{cathode} - E_{anode}$

                                     = 0.916 V - 0.241 V

                                     = 0.675 V

Thus, we can conclude that 0.675 V is the new voltage.