Cell Potential and Gibbs Free Energy: Videos & Practice Problems

Use the electrode potentials tabulated below.

What is the ∆G°_rxn at 25°C for the following reaction?

Cu²⁺(aq)+ Fe(s) →Fe³⁺(aq)+Cu(s)

At 25°C, what are the K_eq and ∆G°_rxn for the disproportionation reaction of liquid hydrogen peroxide to liquid water and oxygen gas?

For the reaction below, determine the standard cell potential and the standard Gibbs free energy (in kJ):

2 Ti(s) + 3 Ge²⁺(aq) → 2 Ti³⁺(aq) + 3 Ge(s)

E°_red (Ti³⁺/Ti) = –1.37 V

E°_red (Ge²⁺/Ge) = +0.24 V

Used in handheld devices, such as smartphones, lithium-ion batteries can deliver a potential of 3.70 V. Calculate the change in Gibbs free energy (ΔG) for the reaction of this cell:

Li(s) + CoO₂(s) → LiCoO₂(s)

For each of the Q/K ratios, identify whether E_cell and ΔG are negative, positive, or zero. 

Q/K ratios: <1, =1, >1

Fluorine is prepared via electrolysis. The following are the half-reactions:

Cathode: 2 H⁺ (aq) + 2e⁻ → H₂ (g)
(E° = 0 V)

Anode: 2 F⁻ (aq) → F₂ (g) + 2e⁻
(E° = −2.87 V)

Find E° and ΔG° for the reaction.

In cellular respiration, molecular oxygen is reduced by NADH to produce water. This reaction is an energy-yielding process in the form of adenosine triphosphate (ATP) Using the following reduction potentials, 

O₂(g) + 4 H⁺(aq) + 4 e⁻ → 2 H₂O(l) E°_red = +0.82 V 

NAD⁺(aq) + H⁺(aq) + 2 e⁻ → NADH (aq)  E°_red = −0.32 V 

At 298 K, what is the ∆G° for the reduction of O₂ by NADH?

Using the following reduction half-reactions: 

Ag⁺(aq) + e⁻ → Ag(s) E°_red = 0.80 V

What is the change in Gibbs free energy for the oxidation of Ag(s) by SO₄²⁻(aq) at 298 K using the following reduction half-reactions?

Determine ∆G°rxn at 25.0 °C using tabulated electrode potentials

La³⁺(aq) + NO(g) + 2 H₂O(l) → La(s) + NO₃^-(aq) + 4 H⁺(aq)

Calculate the Eºcell given that the standard Gibbs free energy of the reaction is -132.0 kJ

A(s) + B³⁺(aq) → A³⁺(aq) + B(s)

The +1 oxidation state is the most stable state for Tl, but it is not as common for Ga. Calculate the standard potential and standard Gibbs free energy (in kJ) for the disproportionation reaction below to explain this phenomenon

3 M⁺(aq) → M³⁺ (aq) + 2 M (s)              M = Ga or Tl

Is the reaction spontaneous for either Ga⁺ or Tl⁺? The relevant standard reduction potentials are listed below

Tl³⁺(aq) + 2 e^-→ Tl⁺ (aq)                  E° = +1.25 V

Tl⁺(aq) + e^-→ Tl (s)                          E° = -0.34 V

Ga³⁺(aq) + 2 e^-→ Ga⁺ (aq)               E° = -0.35 V

Ga⁺(aq) + e^-→ Ga (s)                       E° = -0.20 V

What is the main significance of Gibbs free energy (ΔG) in electrochemical cells?

How does a positive standard cell potential (E°cell) relate to the spontaneity of a reaction and Gibbs free energy?

Given a redox reaction in an electrochemical cell where n = 2 moles of electrons, Faraday's constant (F) is 96485 C/mol, and E°cell is 1.5 V, calculate the standard Gibbs free energy (ΔG°).

What is the role of Faraday's constant in electrochemical reactions, and what are its units?

If 3 moles of electrons pass through an electrochemical cell, what is the total charge transferred using Faraday's constant?

Convert 1500 coulombs to joules given a potential difference of 3 volts.

A battery discharges 2000 coulombs of charge at a potential difference of 12 volts. Calculate the energy change in the battery in joules.

In a redox reaction within an electrochemical cell, which process involves the loss of electrons?

Given a reaction where 3 moles of electrons transfer and the cell potential is 2 V, analyze the connection between Faraday's constant and the total energy change in the cell.