Question

Which cell of the following will measure standard electrode potential of copper electrode?
A) $Pt\left( s \right)|{H_2}\left( {g,0.1\,bar} \right)|{H^ + }\left( {aq,1M} \right)||C{u^{2 + }}\left( {aq,1M} \right)|Cu$
B) $Pt\left( s \right)|{H_2}\left( {g,1\,bar} \right)|{H^ + }\left( {aq,1M} \right)||C{u^{2 + }}(aq,2M)|Cu$
C) $Pt\left( s \right)|{H_2}\left( {g,1\,bar} \right)|{H^ + }\left( {aq,1M} \right)||C{u^{2 + }}\left( {aq,1M} \right)|Cu$
D) $Pt(s)|{H_2}(g,1\,bar)|{H^ + }(aq,0.1M)||C{u^{2 + }}(aq,1M)|Cu$

Answer 1

Hint: In this question, we have to choose the right option for the cell which is used to measure the standard electrode potential of copper electrode. We have to take this in consideration that here standard electrode potential is mentioned. Standard electrode potential is defined as the electrode potential of the individual electrode with respect to a standard electrode at the standard state with ions at an effective concentration of 1M at the standard atmospheric pressure.

Complete step-by-step answer:
We can see common things in all the options. In every option anode is taken to be the standard hydrogen electrode (SHE) while the cathode is the copper electrode. The effective concentration of the copper and the hydrogen ions is different in the options. We know that the effective concentration of all the ions should be unity while measuring the standard electrode potential. Hence, options B and D are wrong.

For a standard hydrogen electrode, the pressure of the hydrogen gas which is bubbled is maintained at a pressure of $1\,bar$. Hence, the option A is incorrect too.

The cell for measuring the standard electrode potential of copper electrode should be represented as follows:
$Pt\left( s \right)|{H_2}\left( {g,1\,bar} \right)|{H^ + }\left( {aq,1M} \right)||C{u^{2 + }}\left( {aq,1M} \right)|Cu$

Hence, option ‘C’ is the correct answer.

Note: There is a difference in electrode potential and standard electrode potential. Electrode potential is the potential difference between the electrode and the electrolyte while standard electrode potential is the electrode potential when the concentration of all the species involved is maintained at unity. Also, the standard electrode potential is measured at standard conditions i.e., at a temperature of $298\,K$and pressure of $1\,atm$and concentrations $ = 1\,M$.