Difference Between Daniell Cell and Galvanic Cell

Main Difference – Daniell cell vs Galvanic Cell

An electrochemical cell is a device that is capable of generating electricity from chemical reactions or facilitating a chemical reaction with electricity. These cells are composed of two half cells. There is an electrode and an electrolyte per each half cell. Sometimes both electrodes are placed in the same container, but the two electrolytes are separated via a porous barrier. Daniell cell and galvanic cell are examples of electrochemical cells. A Daniell cell is a type of electrochemical cell that is composed of copper and zinc electrodes. A galvanic cell is an electrochemical cell that uses electrical energy generated by spontaneous redox reactions. The main difference between Daniell cell and galvanic cell is that Daniell cell uses only copper and zinc as electrodes whereas a galvanic cell can have a variety of metals as electrodes.

Key Areas Covered

1. What is a Daniell Cell
      – Definition, How it Works
2. What is a Galvanic Cell
      – Definition, How it Works
3. What are the Similarities Between Daniell Cell and Galvanic Cell
      – Outline of Common Features
4. What is the Difference Between Daniell Cell and Galvanic Cell
      – Comparison of Key Differences

Key Terms: Copper, Daniell Cell, Electrochemical Cell, Electrode, Electrolyte, Galvanic Cell, Half-Cell, Oxidation, Redox Reactions, Reduction, Voltaic Cell, Zinc

What is a Daniell Cell

Daniell cell is a type of electrochemical cell that is composed of a copper electrode and a zinc electrode immersed in copper (II) sulfate and zinc sulfate, respectively. Therefore, this cell uses two electrolytes. An electrolyte is a substance that can separate into ions when dissolved in water. These ions are capable of conducting electricity through the aqueous solution of that substance.

One half cell of Daniell cell is composed of a copper electrode immersed in a copper (II) sulfate solution, and the other half cell is composed of a zinc electrode immersed in a zinc sulfate solution. There is a redox reaction which provides electrons for electrical conductivity. Zinc is used as the anode. Copper is the cathode. The two half reactions are given below.

Anode :     Zn_(s)   →   Zn⁺²_(aq)   +   2e

Cathode : Cu⁺²_(aq)   + 2e   →   Cu_(s)

In the anode, zinc is oxidized into zinc (II) ion. In the cathode, copper (II) ion is reduced to copper. The total reaction can be given as below.

Zn_(s)    +    Cu⁺²_(aq)       →      Zn⁺²_(aq)     +     Cu_(s)

Figure 1: A Schematic Diagram of Daniell Cell

For the easy demonstration of the cell, the two electrolytes are separated from each other, and a salt bridge is used for the movement of ions. The salt bridge is filled with a compound that does not interfere with the redox reaction that takes place in the cell. But in an actual Daniell cell, a porous barrier is used to separate the two electrolytic solutions. This porous barrier cannot control the movement of copper ions into zinc sulfate and vice versa. This makes it impossible to recharge.

What is a Galvanic Cell

Galvanic cell is a type of electrochemical cell that uses spontaneous redox reactions to generate electrical energy. This is also called a voltaic cell. The cell is composed of two half cells. Each half cell is composed of an electrode and an electrolyte. The electrode is immersed in the electrolytic solution. Sometimes these electrolytes are completely separate, but other times they are separated only by a porous barrier. When the electrolytes are completely separated, a salt bridge is used to maintain the movement of ions between the two electrolytes.

Figure 2: An Example of a Galvanic Cell

The electrodes and electrolytes are chosen considering whether they are spontaneous or not. This can be found theoretically by calculating the electrode potentials of each half cell.  However, one half cell should show oxidation whereas other half cell should show reduction reaction. Oxidation occurs at the anode whereas reduction occurs at the cathode. Since a galvanic (voltaic) cell uses the energy released during a spontaneous redox reaction to generate electricity, galvanic cells are used as sources of electrical energy. They produce direct current.

Similarities Between Daniell Cell and Galvanic Cell

• Both are examples of electrolytic cells.
• Both are composed of half cells that are composed of electrodes and electrolytes.
• Electrolytes can be either completely separate or separated by a porous membrane.

Difference Between Daniell Cell and Galvanic Cell

Definition

Daniell Cell: Daniell cell is a type of electrochemical cell that is composed of a copper electrode and a zinc electrode immersed in copper(II) sulfate and zinc sulfate respectively.

Galvanic Cell: Galvanic cell is a type of electrochemical cell that uses spontaneous redox reactions to generate electrical energy.

Anode

Daniell Cell: Anode of the Daniell cell is a zinc electrode.

Galvanic Cell: Anode of the galvanic cell is a metal that can be oxidized.

Cathode

Daniell Cell: Cathode of the Daniell cell is a copper electrode.

Galvanic Cell: Cathode of the galvanic cell is a metal that can be reduced.

Electrolytes

Daniell Cell: The electrolytes used for the Daniell cell are copper(II) sulfate and zinc sulfate.

Galvanic Cell: The electrolytes used for the galvanic cell are the salts of metals of each electrode.

Conclusion

Both Daniell cell and galvanic cell are electrochemical cells. These cells use spontaneous redox reactions for the generation of electrical energy. This produced energy can be used for an external work to be done. The key difference between Daniell cell and galvanic cell is that Daniell cell uses only copper and zinc as electrodes whereas a galvanic cell can have a variety of metals as electrodes.

References:

1. “Electrochemical Cells.” Chemistry LibreTexts, Libretexts, 18 Apr. 2017, Available here.
2. Helmenstine, Ph.D. Anne Marie. “How Electrochemical Cells Work.” ThoughtCo, Available here.
3. “Daniell cell.” Wikipedia, Wikimedia Foundation, 15 Oct. 2017, Available here.

Image Courtesy:

1. “Daniell cell” By Antimoni – Own work (CC BY-SA 3.0) via Commons Wikimedia (Relabeled)
2. “Galvanic cell unlabeled” By Hazmat2 – Own work (CC BY-SA 3.0) via Commons Wikimedia (Labeled)