Select the correct statement(s) about NHE
This question has multiple correct options
A) ${{E}^{\odot }}$ of NHE is arbitrarily assumed to be zero.
B) ${{E}^{\odot }}$ of NHE is equal to zero.
C) NHE refers as\[\begin{matrix}
   Pt,{{H}_{{{2}_{\left( g \right)}}}}/ & {{H}^{\oplus }} \\
   \left( 1\,bar \right) & a=1 \\
\end{matrix}\] at ${{25}^{\circ }}C$
D) NHE is very susceptible to dissolved${{O}_{2}}$, ${{H}_{2}}S$ and all other reducing agents.

Hint: NHE is also represented as SHE i.e. the standard Hydrogen Electrode.
- SHE or NHE is the reference electrode which helps to identify the reducing agents and oxidizing agents.

Complete step by step answer:
- So in the question various statements about the SHE or NHE are given and we have to sort into, which of them are correct and which of them are incorrect.
- Before that let’s get some idea about Standard Hydrogen Electrode.
- Standard Hydrogen electrode is a redox electrode and it is the reference electrode with respect to which the oxidation and reduction potential of other metals are sorted.
NHE is the Normal Hydrogen electrode, both are similar, the difference is that,
NHE – potential was measured by immersing Pt electrode in the 1N strong acid and the hydrogen gas was bubbled through it.
SHE-Here we Pt electrode in a theoretically ideal solution, here we consider that the concentration of ${{H}^{+}}$ions is 1 M, but the ${{H}^{+}}$ions do not have interactions with other ions.
Now let’s see the statements,
- Option A)
In this statement it is given that, ${{E}^{\odot }}$of NHE is arbitrarily assumed to be zero.
The statement is true since we know that the ${{E}^{\odot }}$value for NHE is not zero, we assumed it to be zero for convenience. And for comparing the electrode potential of other metals, we took the value as zero
So this statement is true.
- Option (B)
Here, it is given as, ${{E}^{\odot }}$ of NHE is equal to zero.
We know this statement is incorrect as we discussed in the previous option, the electrode potential value for Normal Hydrogen Electrode is not zero, we assume it as zero.
So option (B) is incorrect.
- In Option (C), it is the representation of the cell at NTP conditions,
NHE refers as\[\begin{matrix}
Pt,{{H}_{{{2}_{\left( g \right)}}}}/ & {{H}^{\oplus }} \\
 \left( 1\,bar \right) & a=1 \\
\end{matrix}\] at ${{25}^{\circ }}C$
The representation is correct, since we consider the value of NHE at normal temperature and pressure which is at a pressure of 1 atm and a temperature of ${{25}^{\circ }}C$ and molarity will be 1M.
So option (C) is also a correct statement.
- Then the last one option (D), here it is given as NHE is very susceptible to dissolved ${{O}_{2}}$, ${{H}_{2}}S$ and all other reducing agents.
It is also correct as NHE is very much susceptible to dissolved ${{O}_{2}}$, ${{H}_{2}}S$ and all other reducing agents, since they affect the concentration of the ${{H}^{+}}$ ions, the electrode potential also gets affected.
So option (D) is also a correct statement.
So, the correct answer is “Option A,C and D”.

Note: We should know a basic idea of the SHE Or NHE, its representation, construction and about its potential to verify the above statements.
If another statement is SHE is susceptible to electrode poisoning was asked, then it is also a correct statement .As the electrode poisoning will affect the electrode potential.