Question

If Calomel, Nickel and Gold electrodes have standard reduction potential of -0.28, 1.43 and 0.35 V with reference to SHE. Find out oxidation potentials of Nickel, Gold and SHE with reference to Calomel.

Answer 1

Hint: We can find the reduction potential of given electrodes with respect to calomel electrodes by following formula.
\[E = {E^ \circ } - E_{calomel}^ \circ {\text{ }}\]

Complete step by step solution:
SHE stands for standard hydrogen electrode. We will find the potentials of given electrodes with reference to calomel electrodes.
We are given that standard reduction potentials of Calomel, Nickel and Gold electrodes is -0.28, 1.43 and 0.35 V respectively. So,
\[E_{Calomel}^ \circ = - 0.28V \\
E_{Nickel}^ \circ = 1.43V \\
E_{Gold}^ \circ = 0.35V \\
\]
We know that standard reduction potentials of the electrodes are taken with respect to the hydrogen electrode or SHE. We know that the standard reduction of hydrogen electrode is considered 0 V.
We can find the reduction potential of given electrodes with respect to calomel electrodes by following the formula.
\[E = {E^ \circ } - E_{calomel}^ \circ {\text{ }}..{\text{(1)}}\]
For Nickel electrode, we can write equation (1) as
\[{E_{Nickel}} = E_{Nickel}^ \circ - E_{calomel}^ \circ \]
So, \[{E_{Nickel}} = 1.43 - ( - 0.28) = 1.71V\]
Now, the potential obtained is the reduction potential of the electrode because the standard potentials are used here which are reduction potentials. So, we can simply change the sign of the reduction potential of the electrode to obtain oxidation potential of the given electrode.
So, oxidation potential of the Nickel electrode = -1.71 V
For Gold electrode, we can write the equation (1) as
\[{E_{Gold}} = E_{Gold}^ \circ - E_{calomel}^ \circ \]
Thus, we can write that \[{E_{Gold}} = 0.35 - ( - 0.28) = 0.63V\]
- This is the reduction potential. So, oxidation potential of the electrode = -0.63 V
For SHE electrode, we can write equation (1) as
\[{E_{SHE}} = E_{SHE}^ \circ - E_{calomel}^ \circ \]
So, \[{E_{SHE}} = 0 - ( - 0.28)\] = 0.28 V
- So, the oxidation potential of the SHE electrode = -0.28 V.

Note: We can obtain reduction potential from the oxidation potential or oxidation potential from the reduction potential by simply changing the sign of the potential. The reduction potential of the cell is considered as the standard potential of the cell.