Question

For the cell $Zn(s)|Z{n}^{2+}(aq)||M^{x+}(aq)|M(s),$ different half cells and their standard electrode potentials are given below :

$M^{x+}(qa/M(s)$	$A{u}^{3+}(aq)/Au(s)$	$A{g}^{+}(aq)/Ag(s)$	$F{e}^{3+}(aq)/F{e}^{2+}(aq)$	$F{e}^{2+}(aq)/Fe(s)$
$E_{M^{x+}/M^{(v)}}^{\circ }$	1.40	0.80	0.77	-0.44

If $E_{Z{n}^{2+}/Zn}^{\circ }=-0.76V$, which cathode will give a mximum value of $E_{cell}^{\circ }$ per electron transferred ?

• A. $F{e}^{3+}/F{e}^{2+}$
• B. $A{g}^{+}/Ag$
• C. $A{u}^{3+}/Au$
• D. $F{e}^{2+}/Fe$

Answer 1

Answer: (C)

We have,
$E_{\text{cell }}^{\circ }=E_{\text{cathode }}^{\circ }-E_{\text{anode }}^{\circ }$
For a high value of $E_{\text{cell }}^{\circ }$ the value of SRP of cathode should be high.
Here the highest value is for $A{u}^{3+}/Au$
$E_{\text{cell }}^{\circ }=1.4-(-0.76)=2.16V$
Note: Here the transfer of electron in the cell won't affect the $E_{\text{cell }}^{\circ }$ value.