Question

At what concentration of $Cu^{2+}$(aq), will its electrode potential become equal to its standard electrode potential ?

Answer 1

To measure potential of ${ Cu }/{ { Cu }^{ + } }$ connected in galvanic cell

The half-cell reactions and potentials of the spontaneous reaction are as follows:

At Cathode:

${ Cu }_{ (aq) }^{ +2 }\quad +\quad 2{ e }^{ - }\quad \rightarrow \quad { Cu }_{ (g) }$

${ E }^{ \circ }cathode\quad =\quad 0.34\quad V$

At Anode:

${ H }_{ 2(g) }\quad \rightarrow \quad 2{ H }_{ (aq) }^{ + }\quad +\quad 2{ e }^{ - }$

${ E }^{ \circ }\quad anode\quad =\quad 0\quad V$

Overall reaction

${ H }_{ 2(g) }\quad +\quad { Cu }_{ (aq) }^{ 2+ }\quad \rightarrow \quad 2{ H }_{ (aq) }^{ + }\quad +\quad { Cu }_{ (s) }$

${ E }^{ \circ }cell\quad =\quad { E }^{ \circ }cathode\quad -\quad { E }^{ \circ }anode\quad =\quad 0.34\quad V$

Thus the standard electrode potential for the ${ { Cu }^{ 2+ } }/{ Cu }$ couple is 0.34 V

${ E }_{ cell }\quad =\quad { E }_{ \circ }\frac { RT }{ nF } \log { \frac { oxidation }{ reduction } }$

If oxidation = reduction  

Then, RHS will equal to $log1$

We know that, $\log { 1 } \quad =\quad 0$

Finally, ${ E }_{ \circ cell }\quad =\quad { E }_{ cell }$

The electrode potential becomes equal to standard electrode potential when reactants and products ratio is equal.