Nernst Equation

Concept #1: The Nernst Equation reveals the quantitative connection between the concentrations of compounds and cell potential. 

Example #1: Determine the cell potentials of the following concentration cells: 

Ag | Ag⁺ (aq, 0.0010 M) || Cu²⁺ (aq, 1.0 M) | Cu

E_Anode = 0.799 V         E_Cathode = 0.339 V

Example #2: Consider the following electrochemical cell for the question:

Pt  |  KBr(aq, 0.01 M), Br₂(l)  ||  FeBr₂(aq, 1.0M)  |  Fe         

E_Anode = 1.078 V         E_Cathode = - 0.440 V

Determine the spontaneity and cell potential based on the given cell notation. 

Example #3: Consider a standard voltaic cell based on the reaction:

2 H⁺ (aq) + Sn (s) ⇌ Sn²⁺ (aq) + H₂ (g)

Which of the following actions would change the emf of the cell?

a) Increasing the pH at the cathode

b) Lowering the pH at the cathode

c) Increasing [Sn²⁺] at the anode

d) Increasing the hydrogen gas pressure at the cathode

e) All of the above changes will alter the cell potential

Example #4: Consider the following half cell reaction at T = 25. °C

Ni²⁺(aq) + 2 e ^–  →  Ni(s)      E° = – 0.260 V

What will be the value for E°, the half cell potential for standard conditions, for the reaction

2 Ni(s) →   2 Ni²⁺ (aq) + 4 e ^–

a) + 0.52 V          b) + 0.26 V          c) – 0.26 V          d) – 0.52 V