Question

Which of the following set of metal electrodes can be used in the given galvanic cell?
Given:
$M{g}^{2+}\left(aq\right)+2e^{-}\to Mg\left(s\right);E^0=-2.37V$
$C{u}^{2+}\left(aq\right)+2e^{-}\to Cu\left(s\right);E^0=0.34V$
$A{g}^{+}\left(aq\right)+e^{-}\to Ag\left(s\right);E^0=0.80V$

• A. $A-Ag$
  $B-Cu$
• B. $A-Ag$
  $B-Mg$
• C. $A-Mg$
  $B-Ag$
• D. $A-Mg$
  $B-Cu$

Answer 1

Answer: (C), (D)

$A-Mg$

$B-Cu$
In a galvanic cell, chemical energy is converted to electrical energy.
In the given figure, electrons flow from A to B, which means A is anode and B is the cathode.

At anode, oxidation takes place and at cathode, reduction takes place.

Half cell electrodes having higher $E^0$ will undergo reduction reaction and lower $E^0$ will undergo oxidation reaction.
Thus,
In (a), $Mg$ get oxidised and $Cu$ get reduced.
$Mg\left(s\right)+C{u}^{2+}\left(aq\right)\to M{g}^{2+}\left(aq\right)+Cu\left(s\right)$

In (b), $Cu$ will get oxidised and $Ag$ will get reduced. So, this arrangement of electrode does not used in galvanic cell.

In (c), $Mg$ get oxidised and $Ag$ get reduced.
$Mg\left(s\right)+2A{g}^{+}\left(aq\right)\to M{g}^{2+}\left(aq\right)+2Ag\left(s\right)$

In (d), $Mg$ will get oxidised and $Ag$ will get reduced. So, this arrangement of electrode does not used in galvanic cell.