Electrochemical Cell vs Electrolytic Cell
In electro chemistry oxidation, reduction reactions play an important role. In an oxidation reduction reaction, electrons are transferring from one reactant to another. The substance that accepts electrons is known as a reducing agent, where as the substance which gives away the electron is known as the oxidizing agent. Reducing agent is responsible for reducing the other reactant while undergoing oxidation itself. And for oxidizing agent, it is vice versa. These reactions can be divided in to two half reactions, to show separate oxidations and reductions; thus, it shows the number of electrons moving in or out.
Electrochemical cell is a combination of a reducing and oxidizing agent, which is physically separated from each other. Usually separation is done by a salt bridge. Although they are physically separated, both half cells are in chemical contact with each other. Electrolytic and galvanic cells are two types of electrochemical cells. In both electrolytic and galvanic cells, oxidation-reduction reactions are taking place. Therefore, in an electrochemical cell, there are two electrodes called anode and cathode. Both electrodes are externally connected with a high resistant voltmeter; therefore, current won’t be transmitting between the electrodes. This voltmeter helps to maintain a certain voltage between the electrodes where oxidation reactions takes place. Oxidation reaction takes place on the anode, and the reduction reaction takes place on the cathode. Electrodes are immersed in separate electrolyte solutions. Normally, these solutions are ionic solutions related to the type of electrode. For example, copper electrodes are immersed in copper sulfate solutions and silver electrodes are immersed in silver chloride solution. These solutions are different; hence, they have to be separated. The most common way to separate them is a salt bridge. In an electrochemical cell, the potential energy of the cell is converted to an electrical current, which we can use to light a bulb, or to do some other electrical work.
This is a cell, which uses an electrical current to break chemical compounds, or in other words, to do an electrolysis. Therefore, electrolytic cells need an external source of electrical energy for operation. For an example, if we take copper and silver to be the two electrodes in the cell, silver is connected to the positive terminal of an external energy source (a battery). Copper is connected to the negative terminal. Since the negative terminal is electron rich, electrons flow from there to the copper electrode. So copper is reduced. At the silver electrode, an oxidation reaction takes place, and the released electrons are given to the electron deficient positive terminal of the battery. Following is the overall reaction taking place in an electrolytic cell, which has copper and silver electrodes.
2Ag(s)+ Cu2+ (aq)⇌2 Ag+ (aq)+ Cu(s)
What is the difference between electrochemical cell and electrolytic cell?
• Electrolytic cell is a type of electrochemical cell.
• Electrolytic cells need external current for operation. But an electrochemical cell, the potential energy of the cell is converted to an electrical current. So in an electrolytic cell, the process at the electrodes is not spontaneous.
• In an electrochemical cell, the cathode is positive, and the anode is negative. In an electrolytic cell, the cathode is negative, and the anode is positive.