Question

A galvanic (voltaic) cell consists of an electrode composed of manganese in a 1.0 M manganese(II) ion solution and a second electrode composed of cobalt in a 1.0 M cobalt(II) ion solution, connected by a salt bridge. Calculate the standard potential for this cell at 25 ∘C . Use this list of standard reduction potentials.

Answer 1

Answer : The standard potential for the given cell is 0.9 V

Explanation :

The standard reduction potentials for zinc and copper are:

$E^o_{(Mn^{2+}/Mn)}=-1.18V\\E^o_{(Co^{2+}/Co)}=-0.28V$

The substance having highest positive $E^o$ potential will always get reduced and will undergo reduction reaction.

Here, cobalt will undergo reduction reaction will get reduced. Manganese will undergo oxidation reaction and will get oxidized.

Oxidation half reaction:  $Mn\rightarrow Mn^{2+}+2e^-$

Reduction half reaction:  $Co^{2+}+2e^-\rightarrow Co$

Oxidation reaction occurs at anode and reduction reaction occurs at cathode.

To calculate the $E^o_{cell}$ of the reaction, we use the equation:

$E^o_{cell}=E^o_{cathode}-E^o_{anode}$

$E^o_{cell}=E^o_{(Co^{2+}/Co)}-E^o_{(Mn^{2+}/Mn)}$

Putting values in above equation, we get:

$E^o_{cell}=(-0.28V)-(-1.18)=0.9V$

Hence, the standard potential for the given cell is 0.9 V