Difference Between Galvanic and Electrolytic Cell

Main Difference – Galvanic vs Electrolytic Cell

In physical chemistry, a cell is a system that is used to relate chemicals with electricity. In other words, cells can either be used to produce an electric current from chemical compounds or to apply electric current for the completion of a chemical reaction. Galvanic cells and electrolytic cells are good examples of such cells. Galvanic cell is also called electrochemical cell. Both these cells involve a solution composed of ions that are capable of conducting electricity and electrodes to measure the potential of that solution. The main difference between a Galvanic and electrolytic cell is that a Galvanic cell converts chemical energy into electrical energy whereas an electrolytic cell converts electrical energy into chemical energy.

Key Areas Covered

1. What is a Galvanic Cell
      – Definition, Explanation of the Technique
2. What is an Electrolytic Cell
      – Definition, Explanation of the Technique
3. What is the Difference Between Galvanic and Electrolytic Cell
     – Comparison of Key Differences

Key Terms: Electrochemical Cell, Electrode, Electrolyte, Electrolytic Cell, Galvanic Cell

What is a Galvanic Cell

A Galvanic cell is an electrochemical cell that can produce electricity with the help of a chemical reaction. This chemical reaction is a redox reaction which includes an oxidation reaction and a reduction reaction that occur at the same time. But these oxidation and reduction reactions are taking place in two separate solutions.

Typically, a cell is composed of two half cells. Each half cell is composed of an electrode immersed in a solution containing the metal salt that corresponds to that electrode. The two half-cells are connected to each other through a wire. The two solutions are connected to each other by a salt bridge.

A Galvanic cell is composed of two metal electrodes that are immersed in two solutions. Each metal electrode is immersed in solutions containing dissolved salts of each metal. For example, if the two metal electrodes are copper and zinc, the copper electrode can be immersed in a copper sulfate solution whereas the zinc electrode can be immersed in a zinc sulfate solution. Sometimes, these two solutions are completely separated from each other. Here the two solutions are connected through a salt bridge. But sometimes, the two solutions are separated from a porous disk. Then the ions can move through these pores.

Figure 1: A Galvanic Cell

The two electrodes are externally connected to each other through a piece of wire. This wire can be connected to a voltmeter in order to measure and control the potential of the cell. Zinc metal readily loses electrons. Therefore, Zn atoms of the zinc electrode can release electrons, becoming positively charged cations. Then these Zn⁺² ions are released to the solution that the electrode is immersed in. This causes the mass of the zinc electrode to get reduced.

The electrons that are released from zinc atoms are moved to the copper solution through the external circuit. The copper ions in the solution can get these electrons and become copper atoms. These copper atoms get deposited on the copper electrode. Therefore, the mass of the copper electrode is increased. Likewise, the chemical reaction that occurs in the system causes the creation of an electric current through the external wire. Therefore, Galvanic cell is known to be converting chemical energy into electrical energy. Here the anode is negative, and the cathode is positive since the oxidation reaction occurs in the anode, and the reduction reaction occurs in the cathode.

What is an Electrolytic Cell

An electrolytic cell is a cell that uses an electric current for the progression of a chemical reaction. An electrical current is used in these cells to obtain a non-spontaneous reaction. This is the opposite of the Galvanic cell. The spontaneous redox reactions that occur in the galvanic cell can be reversed by applying a voltage in electrolytic cells.

The process done by the electrolytic cell is known as electrolysis. The anode of the electrolytic cell is positively charged, and the cathode is negatively charged. The oxidation reaction occurs in the cathode whereas the reduction reaction occurs in the anode.

Figure 2: An Electrolytic Cell

For example, if we use Zn electrode and Cu electrode, we can obtain the reverse process of the above by applying a suitable voltage. Then Zn will be deposited on the Zn electrode, and Cu electrode will reduce its mass by oxidation. However, in electrolytic cells, the two electrodes are immersed in the same electrolytic solution.

Difference Between Galvanic and Electrolytic Cell

Definition

Galvanic Cell: A Galvanic cell is an electrochemical cell that can produce electricity with the help of a chemical reaction.

Electrolytic Cell: An electrolytic cell is a cell that uses an electric current for the progression of a chemical reaction.

Technique

Galvanic Cell: A Galvanic cell converts chemical energy into electrical energy.

Electrolytic Cell: An electrolytic cell converts electrical energy into chemical energy.

Chemical Reaction

Galvanic Cell: In Galvanic cells, a spontaneous reaction occurs.

Electrolytic Cell: In electrolytic cells, a non-spontaneous reaction occurs.

Anode and Cathode

Galvanic Cell: In Galvanic cell, the anode is negatively charged, and the cathode is positively charged.

Electrolytic Cell: In electrolytic cell, the anode is positively charged, and the cathode is negatively charged.

Conclusion

Galvanic cells and electrolytic cells are systems that are used to relate the electricity with chemical compounds. These cells can covert either chemical energy into electrical energy or electrical energy into chemical energy. The main difference between Galvanic cell and electrolytic cell is that a Galvanic cell converts chemical energy into electrical energy whereas an electrolytic cell converts electrical energy into chemical energy.

References:

1. “Electrolytic Cells.” Chemistry LibreTexts, Libretexts, 21 July 2016, Available here. Accessed 20 Sept. 2017.
2. “Electrolytic Cells.” Hyperphysics, Available here. Accessed 20 Sept. 2017.
3. GROUP, H2T13 CHEMISTRY. “CHEMISTRY.” ELECTROLYTIC CELL VS GALVANIC CELL, 1 Jan. 1970, Available here. Accessed 20 Sept. 2017.

Image Courtesy:

1. “Galvanic cell labeled”.The original uploader was Elo 1219 at English Wikibooks – Transferred from en.wikibooks to Commons (CC BY 3.0) via Commons Wikimedia
2. “Chemical Principles Fig 1.9” The original uploader was Elo 1219 at English Wikibooks – Transferred from en.wikibooks to Commons. (CC BY 3.0) via Commons Wikimedia