A voltaic cell is constructed with two Zn2+-Zn electrodes, where the half-reaction is Zn2+ + 2e− → Zn (s) E° = -0.763 V The concentrations of zinc ion in the two compartments are 4.50 M and 1.11 ⋅ 10−2 M, respectively. The cell emf is ________ V.

Respuesta :

Answer : The cell emf for this cell is 0.077 V

Solution :

The balanced cell reaction will be,  

Oxidation half reaction (anode):  [tex]Zn(s)\rightarrow Zn^{2+}+2e^-[/tex]

Reduction half reaction (cathode):  [tex]Zn^{2+}+2e^-\rightarrow Zn(s)[/tex]

In this case, the cathode and anode both are same. So, [tex]E^o_{cell}[/tex] is equal to zero.

Now we have to calculate the cell emf.

Using Nernest equation :

[tex]E_{cell}=E^o_{cell}-\frac{0.0592}{n}\log \frac{[Zn^{2+}{diluted}}{[Zn^{2+}{concentrated}]}[/tex]

where,

n = number of electrons in oxidation-reduction reaction = 2

[tex]E_{cell}[/tex] = ?

[tex][Zn^{2+}{diluted}][/tex] = 0.0111 M

[tex][Zn^{2+}{concentrated}][/tex] = 4.50 M

Now put all the given values in the above equation, we get:

[tex]E_{cell}=0-\frac{0.0592}{2}\log \frac{0.0111M}{4.50M}[/tex]

[tex]E_{cell}=0.077V[/tex]

Therefore, the cell emf for this cell is 0.077 V