Electrochemical Cells
Introduction
Electrochemical cells convert chemical energy to electrical energy or vice versa using redox reactions. They are central to batteries, fuel cells, corrosion processes, electroplating and industrial electrochemistry.
Types of Electrochemical Cells
- Galvanic (Voltaic) Cells: Generate electrical energy from spontaneous redox reactions (e.g., Daniell cell, lead–acid battery).
- Electrolytic Cells: Consume electrical energy to drive non-spontaneous chemical reactions (e.g., electrolysis, electroplating).
Components of a Galvanic Cell
- Anode: Electrode where oxidation occurs; electrons are released.
- Cathode: Electrode where reduction occurs; electrons are accepted.
- Electrolyte: Ionic solution allowing ion transport around electrodes.
- Salt bridge: U-shaped conduit (e.g., KCl, agar + salt) that maintains electrical neutrality by allowing ion flow between half-cells.
Working Principle
In a galvanic cell oxidation at the anode releases electrons that flow through an external circuit to the cathode, producing current. The salt bridge permits ions to flow to balance charges produced by electron flow.
Example: Daniell Cell
The Daniell cell uses a zinc electrode in ZnSO4 and a copper electrode in CuSO4. Half-reactions:
- Anode (oxidation): Zn (s) → Zn²⁺ (aq) + 2e⁻
- Cathode (reduction): Cu²⁺ (aq) + 2e⁻ → Cu (s)
Tip: Add a labeled Daniell cell diagram (OG image: 1200×630) to this section for better visual learning and social sharing.
Electrolytic Cells
Electrolytic cells require external power to drive non-spontaneous reactions. Common uses include electroplating, water electrolysis (H₂ + O₂ production), and metal refining.
Applications of Electrochemical Cells
- Batteries & portable power
- Electroplating and metal finishing
- Corrosion control (cathodic protection)
- Fuel cells for clean energy
Quiz: Short-Answer (with explanations)
- Answer & explanation Galvanic cells produce electrical energy from spontaneous reactions; electrolytic cells use electrical energy to drive non-spontaneous chemical changes.
- What is the main difference between galvanic and electrolytic cells?
- In a galvanic cell, where does oxidation occur?
- Answer Oxidation occurs at the anode.
- What is the purpose of a salt bridge?
- Answer To maintain electrical neutrality by allowing ion exchange between half-cells, preventing charge buildup.
- Write the oxidation and reduction half-reactions in a Daniell cell.
- Answer Oxidation: Zn → Zn²⁺ + 2e⁻. Reduction: Cu²⁺ + 2e⁻ → Cu.
- Give two applications of electrochemical cells.
- Answer Batteries (portable power) and electroplating/electrolysis (industrial chemistry).
MCQs (Answers included)
- In a galvanic cell, the anode is:
a) Negative electrode b) Positive electrode c) Neutral electrode d) Salt bridge - The salt bridge is used to:
a) Generate electricity b) Oxidize the metal c) Maintain charge balance d) Deposit metal - Which of the following is NOT a galvanic cell?
a) Daniell cell b) Electrolytic cell c) Lead–acid battery d) Zinc–carbon cell - In the Daniell cell, copper undergoes:
a) Oxidation b) Reduction c) No change d) None of these - Electron flow in the external circuit is from:
a) Cathode to anode b) Anode to cathode c) Salt bridge to electrodes d) Electrolyte to electrodes
MCQ Answers
- a) Negative electrode
- c) Maintain charge balance
- b) Electrolytic cell
- b) Reduction
- b) Anode to cathode
Frequently Asked Questions
Q: What is a galvanic cell?
A galvanic cell converts chemical energy into electrical energy using spontaneous redox reactions between two half-cells.
Q: How does the salt bridge stop charge build-up?
By allowing inert ions (e.g., K⁺ and Cl⁻) to migrate and neutralize excess charges in each half-cell so the redox reactions can continue.
Q: Can electrolytic and galvanic cells be the same hardware?
Yes — the same physical cell can operate as galvanic or electrolytic depending on whether it runs spontaneously or with applied external potential (polarity & voltage).
