Question

How many electrons would be transferred in either a voltaic or electrolytic cell that uses the following half reactions

Answer 1

Answer:

Numbers of electrons transferred in the electrolytic or voltaic cell is 6 electrons.

Explanation:

$Fe^{3+} (aq) + 3 e^-\rightarrow Fe (s) ,E^o = -0.036 V$

$Mg^{2+}(aq) + 2 e^- \rightarrow Mg (s),E^o = -2.37 V$

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

Reduction : cathode

$Fe^{3+} (aq) + 3 e^-\rightarrow Fe (s) ,E^o = -0.036 V$..[1]

Oxidation: anode

$Mg(s)\rightarrow Mg^{2+}(aq) + 2 e^-,E^o = 2.37 V$..[2]

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

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

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

$E^o_{cell}=-0.036V-(-2.37 V)=2.334 V$

The overall reaction will be:

2 × [1] + 3 × [2] :

$2Fe^{3+} (aq) + 3Mg(s)+6e^-\rightarrow 2Fe (s)+3Mg^{2+}(aq)+6e^-$

Electrons on both sides will get cancelled :

$2Fe^{3+} (aq) + 3Mg(s)\rightarrow 2Fe (s)+3Mg^{2+}(aq)$

Numbers of electrons transferred in the electrolytic or voltaic cell is 6 electrons.