Electrochemistry and Batteries

Introduction to Electrochemistry

• Controlled flow of electrons enables modern technology (e.g., laptops, phones, pacemakers).
• Electrochemistry involves reactions that produce or consume free electrons—oxidation or redox reactions.
• Redox reactions involve the exchange of electrons.

Redox Reactions and Voltage

• Work depends on the electrical potential or voltage of a reaction.
• High voltage means each electron can do more work.

Battery Mechanics

• Batteries harness energy from redox reactions by placing a device between electron-donating and electron-accepting halves.
• Redox reactions consist of two parts: electron release and electron acceptance.
• Half reactions describe these processes separately.
• Example: In alkaline batteries, zinc reacts with manganese dioxide to form manganese III oxide and zinc oxide.

Alkaline Battery Construction

• Zinc is oxidized; manganese is reduced.
• Two electrons are released per zinc atom; one is consumed per manganese IV atom.
• Potassium hydroxide provides water and hydroxide ions.

Battery Design

• Half reactions are isolated to prevent spontaneous equilibrium and heat release.
• Anode (positive) and cathode (negative) terminals allow electron flow when connected.

Galvanic Cells

• Alkaline batteries are galvanic cells, generating electrical energy from redox reactions.
• Metal rods (anode and cathode) in solution enable electron flow and metal deposition.
• A salt bridge allows ions to move between anode and cathode, completing the circuit.

Calculating Voltage

• Voltage is determined by the difference in chemical demand for electrons in half reactions.
• Standard reduction potential measures potential under standard conditions (25°C, 1M solutions).
• Reference point: hydrogen ion reduction is zero volts.
• Example: Copper reduction potential is +0.34 volts; zinc is -0.76 volts (reversed for oxidation).
• Standard cell potential is the sum of the potentials of both half reactions.

Relation to Equilibrium and Gibbs Free Energy

• Reaction voltage relates to equilibrium constant and Gibbs free energy.
• Positive voltage indicates spontaneous reactions under standard conditions.

Electroplating and Electrolysis

• Electroplating: non-spontaneous reaction using electrolytic cell.
• An electric current causes metal deposition on objects (e.g., chrome plating on iron).
• Electrolysis breaks down molecules in solution for metal deposition.
• Applications include jewelry plating, metal refining, and splitting water into hydrogen and oxygen.

Conclusion

• Electrochemical reactions are crucial in powering electrical devices and have numerous applications in daily life.

Acknowledgments

• Episode contributors include Edi Gonzalez (writer), Blake de Pastino (editor), Dr. Heiko Langner (consultant), Nicolas Jenkins (director), Michael Aranda (sound designer), and Thought Cafe (graphics team).