S17E2 - Cell Potential Calculations and Line Notation

SECTION 17 - Electrochemistry

How to Calculate Galvanic Cell Potentials (Ecell)

We must first consider the standard reduction potentials for each half-reaction:

  ➞  E°cell

  ➞  values are listed in Table 17-1 of my *Chemistry Video Notes,* and also below...

Table 17-1 = Standard Reduction Potentials (in Volts) at 25°C (298K) for Many Common Half-Reactions.

Table of Standard Reduction Potentials
Standard Reduction Potentials Table


ex:  Why is the voltage 1.10 V in the redox reaction occurring in the galvanic cell below?

Galvanic Cell Set Up

The overall balanced redox equation is:

   Zn(s)   +   Cu2+(aq)   →   Cu(s)   +   Zn2+(aq)

Zn-Cu Redox Reaction Example

Anode - where oxidation occurs:    

   Zn   →   Zn2+   +   2e-   ;   E°Zn = + 0.76 V  (from Table 17-1)

Cathode - where reduction occurs:    

   Cu2+   +   2e-   →   Cu   ;   E°Cu2+ = + 0.34 V  (from Table 17-1)


So, overall we have:

   E°cell  =  E°Zn  +  E°Cu2+

Cell Potential Formula Equation

NOTE:  If the half-reaction is reversed in Table 17-1, you must change the sign (+/-) of E°, but if the half-reaction is multiplied through by an integer, the value of E° doesn't change!!


Cell Potential Calculations (Ecell)

ex:  Calculate the overall cell potential of the following reaction:

     Cu(s)   +   2Fe3+(aq)   →   Cu2+(aq)   +   2Fe2+(aq)

  ➞ break up into half-reactions...

Oxidation-Reduction Half Reaction Method


Line Notation

When describing a galvanic cell (electrochemical cell), line notation is used.

    ➞ the anode compartment is listed on the LEFT.
    ➞ the cathode compartment is listed on the RIGHT.

ex:  A few sample problems back, we had an example with zinc and copper:

   Zn(s)   +   Cu2+(aq)   →   Cu(s)   +   Zn2+(aq)

Here it is again, in an easy-to-follow handwritten format...

Line Notation Examples


In my next post on SECTION 17 - Electrochemistry, my 3rd article on this subject,

We'll do more galvanic cell examples and practice balancing half-reactions and calculating E°cell.

Be sure to check it out!...