Question

Which of the following is/are true for standard hydrogen electrode?

• A. The hydrogen ion concentration is $1M$
• B. Pressure of hydrogen is 1 bar
• C. Pure $H_2$ gas is bubbled into acidic solution
• D. All of the above.

Answer 1

The correct option is D All of the above.

Hydrogen is used as standard electrode and other electrode's potential is measured with respect to hydrogen so potential of hydrogen is arbitrarily assumed to be zero for standard measurements.

Standard hydrogen electrode:
It consist of a platinum electrode coated with platinum black dipped in an acidic solution of $1MHCl$ and pure hydrogen gas is bubbled at $1bar$ into the solution.

Pure $H_2$ gets adsorbed at $Pt$ surface and be in contact with $H^{+}$ ions in the solution.

Here,
Concentration of $H^{+}$ ion solution should be $1M$
Pressure of $H_2$ should be $1bar$
The potential of standard hydrogen electrode is assumed to be zero at ${25}^{\circ }C$

The redox half cell of SHE is where the following reaction takes place:
$H^{+}\left(aq\right)+e^{-}\rightleftharpoons \frac{1}{2}{H}_2\left(g\right)$
Cell Representation :
$H^{+}(aq,1M)|H_2(g,1bar)|Pt\left(s\right)$