Question

The potential of a hydrogen electrode is -118.5 mV. The ${{H}^{+}}$ concentration of the solution is:
A. 0.01 M
B. 2 M
C. ${{10}^{-4}}$M
D. 1 M

Answer 1

An electrode can be defined as an electrical conductor used to make contact with the non-metallic part of that circuit. Whether in an electrochemical cell electrode is referred by the name anode and cathode whereas anode where oxidation occurs and cathode where reduction occurs.

Complete answer:
Electrode potential in electrochemistry can be defined as the electromotive force abbreviated as EMF of a galvanic cell built from standard reference electrode generally with the other electrode to be characterized. By convention the reference electrode is the standard hydrogen electrode which is generally used in abbreviated form SHE. Electrode potential is defined to have a value of zero volts and denoted by E.
Now potential of hydrogen electrode is given i.e.
$E=-118.5mV=118.5\times {{10}^{-3}}V$
We know that the value of ${{E}_{cell}}$can be calculated with the formula
${{E}_{cell}}=\dfrac{0.591}{n}\log [{{H}^{+}}]$
The value of ${{E}_{cell}}$is given and n =1 in this case, now by putting all the values in the above equation we can easily find out the value of ${{H}^{+}}$which can be shown as below:
$\log [{{H}^{+}}]=\dfrac{-118.5\times {{10}^{-3}}}{0.0591}$
$\log [{{H}^{+}}]=-2.0051$
Now by taking the antilog of -2.0051 we can find the value of ${{H}^{+}}$which would be
$[{{H}^{+}}]=0.01M$

Thus from the above discussion we can say that option A is the correct answer.

Note:
Electrode potential appears at the interface between an electrode and electrolyte this is due to the transfer of charged species across the interface, specific adsorption of ions at the interface, and specific adsorption/orientation of polar molecules, including those of the solvent.