How can I use the Nernst equation to calculate the free energy change for oxidation reduction reactions?
There are five steps for calculating the free energy change for an oxidation-reduction reaction. You use the Nernst equation at Step 4.
Calculate the free energy change for the following electrochemical cell at 25.0 °C.
Zn(s) | Zn²⁺ (1.50 mol/L) || Cu²⁺ (0.250 mol/L) | Cu(s)
Step 1. Calculate the standard cell potential,
Zn → Zn²⁺ + 2 e⁻;
Cu²⁺ + 2 e⁻ → Cu;
Zn + Cu²⁺ → Zn²⁺ + Cu;
Step 2. Determine the number of moles of electrons
Step 3. Calculate the reaction quotient,
Step 4. Use the Nernst equation to calculate the nonstandard cell potential,
1.101 V – 0.0230 V = 1.078 V
Step 5. Calculate the free energy.