[Chemistry Class Notes] on Difference Between Galvanic Cells and Electrolytic Cells Pdf for Exam

A cell in chemistry is used to convert chemical energy to electrical energy or we can say for the purpose of conversion of energy. The chemical reactions occur inside the cells and as a result of these, electrical current flows. In this article, we will study about two main cells; these are galvanic cells and electrolytic cells in detail. The chemical energy is converted into electrical energy in galvanic cells while electrical energy is converted into chemical energy into electrolytic cells. These electrochemical cells are used for different applications.

What are Galvanic Cells?

Galvanic cells consist of two half-cells, which convert the chemical potential energy into electrical potential energy. It happens through a spontaneous chemical reaction. On the two half-cells of galvanic cells, each half-cell contains an electrode in an electrolyte. The separation is required to prevent a direct chemical contact of the reduction and oxidation reactions by creating a potential difference. Electrons that are released in the oxidation reaction passes through an external circuit before it is being used by the reduction reaction.

Working of Galvanic Cells

The working of galvanic cells is very simple. It involves a chemical reaction that allows the electrical energy to use as an end product. During a redox reaction, the galvanic cell uses the energy transfer between electrons to convert chemical energy into electrical energy. Reactions of Daniel cell (galvanic cell) at cathode and anode are as follows:

At cathode: Cu²⁺ + 2e⁻→ Cu

At anode: Zn → Zn²⁺ + 2e⁻

The galvanic cell has the power to separate the flow of electrons through the cycle of oxidation and reduction, creating a half-reaction and connecting both of them to a wire such that a path may be created for the flow of electrons across that wire. This kind of electron flow is essentially called a current. And, such current can be made to pass through a wire to complete a circuit and to obtain the output in any device like a wristwatch, a television, and so on.

The galvanic cell may be composed of any two metals. If left in contact with each other, these two metals will form an anode and a cathode. This combination makes the galvanic corrosion more anodic. A connecting circuit is necessary to prevent this corrosion.

Terms to Remember

A few of the important terms brought into use in galvanic cells are mentioned below.

• Phase Boundaries, which refers to two metals acting as a cathode and anode.

• Salt Bridge, a connecting medium that allows a redox reaction to occur.

• Oxidation and reduction, a chemical process that allows the electric current to form and pass through a galvanic cell. 

What are Electrolytic Cells?

Electrolytic cells are much the same as galvanic cell as it requires a salt bridge, two electrodes in addition to the flow of electrons from the anode to the cathode. However, still, the two electrodes manage to differentiate from others in various aspects. For one, the electrolytic cell transforms electrical energy into chemical energy and, not the other way round.

Working of Electrolytic Cells

With the help of an electrolysis cell, molten sodium chloride (which contains dissociated Na+ cations and Cl^– anions) can be electrolyzed.

In the figure given below, two inert electrodes are dipped into molten sodium chloride. The cathode becomes rich in electrons when the electric current passes through it and develops a negative charge. The positively charged Na+ are attracted towards the negatively charged cathode. 

The atoms of chlorine move towards the positively charged cathode. The chlorine gas is formed at the anode as a result of this. The chemical equations and the overall cell reaction are as follows:

Reaction at Cathode: [Na⁺ + e⁻ → Na] x 2

Reaction at Anode: 2Cl⁻ → Cl2 + 2e⁻

Cell Reaction: 2NaCl → 2Na + Cl₂

Process of Electrolysis

In simple terms, the process of electrolysis refers to the decomposition of an element that is provided under the influence of an electric current. The first electrolysis was conducted by Sir Humphrey Davey, in 1808. This analysis provided important knowledge into how other elements act and how they vary from compounds and ions.

The subsequent redox reaction in the process is not natural, so for the start-up reaction, electrical energy must be added to the apparatus. Unlike the galvanic cell, the electrolytic cell requires both metals to be positioned in the same container. In this case, the positive electrode is considered an anode, and the negative electrode is considered a cathode.

What is an Electrochemical Cell?

An electrochemical cell is a device that would generate electrical energy by performing the chemical reactions in it or using the electrical energy supplied to it, facilitating chemical reactions in it. These devices have the capability to convert electrical energy into chemical energy and vice versa.

A good example of an electrochemical cell is a standard 1.5 Volt battery used to power up many electrical devices like a TV remote, a wall clock, and more.

Such types of cells are capable of generating electricity forming the chemical reactions in them, these types of cells are called Galvanic Cells or Voltaic Cells. As an alternative, cells that cause chemical reactions to happen in them when an electrical current is passed through them are referred to as electrolytic cells.

Difference Between Galvanic Cells and Electrolytic cells

There are numerous differences between galvanic and electrolytic cells to explain. Some of them are tabulated below.

Conclusion

From the above differences between galvanic and electrolytic cells, we can conclude that a galvanic cell produces an electric current with a chemical reaction that happens spontaneously in it, whereas an electrolytic cell does the opposite. This means it brings about the chemical reaction using an electric current from an external source.