5.4.2 Standard Cell Potential: Calculations, Electron Flow & Feasibility

Once the standard electrode potentials (E^ꝋ) of the half-cells are determined, the standard cell potential (E_cell^ꝋ) can be calculated by subtracting the less positive E^ꝋ from the more positive E^ꝋ value

• The half-cell with the more positive E^ꝋ value will be the positive pole
  • The positive electrode or cathode is the one which most favours reduction

• The half-cell with the less positive E^ꝋ value will be the negative pole
  • The negative electrode or anode is the one which most favours oxidation

Worked example: Calculating the standard cell potential

Answer

• Step 1: Calculate the standard cell potential

E_cell^ꝋ = (+0.34) - (-0.76) = +1.10 V

The voltmeter will therefore read off a value of 1.10 V

• Step 2: Determine the positive and negative poles

  The Cu²⁺/Cu  half-cell is the positive pole as its E^ꝋ is more positive than the E^ꝋ value of the Zn²⁺/Zn half-cell

To show the processes taking place in the cell to further explain

Ionic equations in the cell