Galvanic Cell vs Electrolytic Cell: Differences & Real-World Examples

Galvanic vs. Electrolytic Cells: JEE Main Electrochemistry

Explore the fundamental differences between galvanic and electrolytic cells, their working principles, and real-world applications, crucial for JEE Main electrochemistry.

Concept Overview

This question tests the understanding of the fundamental differences between galvanic (voltaic) cells and electrolytic cells, which are core topics in electrochemistry. It requires distinguishing them based on their energy conversion (chemical to electrical vs. electrical to chemical), spontaneity of reactions, and the sign conventions for the anode and cathode. Understanding these distinctions is vital for solving various problems related to electrolysis and electrochemical cells.

Step 1: Define Galvanic Cell and its Working Principle

A galvanic cell, also known as a voltaic cell, is an electrochemical cell that converts chemical energy into electrical energy through a spontaneous redox reaction. In a galvanic cell, the anode is the electrode where oxidation occurs, and it is the negative terminal. The cathode is the electrode where reduction occurs, and it is the positive terminal. The spontaneous flow of electrons from the anode to the cathode through an external circuit generates an electric current.

Step 2: Define Electrolytic Cell and its Working Principle

An electrolytic cell is an electrochemical cell that converts electrical energy into chemical energy by driving a non-spontaneous redox reaction using an external source of electrical energy (like a battery or power supply). In an electrolytic cell, the anode is where oxidation occurs, and it is the positive terminal (connected to the positive terminal of the external power source). The cathode is where reduction occurs, and it is the negative terminal (connected to the negative terminal of the external power source).

Step 3: Summarize Key Differences in a Table

Step 4: Real-World Examples of Galvanic Cells

Galvanic cells are commonly found in batteries. For instance, a dry cell battery (like those used in remote controls or flashlights) is a galvanic cell where zinc and manganese dioxide undergo a spontaneous redox reaction to produce electricity. Another example is a lead-acid battery used in cars, which consists of lead and lead dioxide electrodes in sulfuric acid, generating electricity through spontaneous reactions during discharge.

Step 5: Real-World Examples of Electrolytic Cells

Electrolytic cells are used in processes that require forcing non-spontaneous chemical reactions. A prime example is the electrolysis of water to produce hydrogen and oxygen gas, which requires an external power source. Another significant application is electroplating, where a thin layer of a metal (like chromium or nickel) is deposited onto another object (like cutlery or car parts) using an electrolytic cell to provide a protective or decorative coating. The Downs process for the production of sodium metal from molten sodium chloride is also an electrolytic process.

Key Takeaways:

• Galvanic cells convert chemical energy to electrical energy via spontaneous redox reactions, while electrolytic cells use electrical energy to drive non-spontaneous redox reactions.
• In galvanic cells, the anode is negative and the cathode is positive; in electrolytic cells, the anode is positive and the cathode is negative.
• Batteries (like dry cells and lead-acid batteries) are examples of galvanic cells, while processes like electrolysis of water and electroplating utilize electrolytic cells.
• The spontaneity of the reaction ($Delta G$) is negative for galvanic cells and positive for electrolytic cells.

Answer: Galvanic cells convert chemical energy to electrical energy through spontaneous redox reactions (anode is negative, cathode is positive), e.g., batteries. Electrolytic cells use electrical energy to drive non-spontaneous redox reactions (anode is positive, cathode is negative), e.g., electroplating, electrolysis of water.