Question

What Is Agar Agar in Salt Bridge?

Answer 1

Hint: Agar-agar is a jelly-like substance that is extracted from red algae. Agar-agar has multiple uses from culinary to scientific. It is used in a part of an electrochemical cell called the salt bridge. The purpose of the salt bridge is to connect the oxidation and reduction half-cells and maintain electrical neutrality within them.

Complete Step by Step Solution:
Agar-agar is obtained from the cell walls of certain species of red algae known as agarophytes. It consists of a mixture of polysaccharides, agarose and agaropectin. The mixture has 70% agarose. Agarose is a linear polymer consisting of agarobiose monomer units.

Agaropectin is a heterogeneous mixture of smaller molecules that are present in lesser amounts. Agar-agar supports the cell wall in agarophytes.
Agar-agar has multiple uses as a culinary ingredient and in the scientific world also. It acts as a solid substrate for containing culture media which is used in microbiology. Most importantly for us, agar-agar is used in the construction of a component of the electrochemical cell called the salt bridge.

A salt bridge is a device used to connect the reduction and oxidation half-cells of an electrochemical cell. A salt bridge usually consists of a strong electrolyte such as Silver nitrate (\[AgN{O_3}\]) or Potassium chloride (\[KCl\]). The electrolytes chosen must be inert i.e., they must not react with any of the chemicals used in either half-cell. Agar-agar acts as the medium in which the electrolyte is present in the salt bridge. Agar-agar is chosen as the medium because it is a nonelectrolyte hence, it does not dissociate and react with the chemicals present in the half-cells.

The salt bridge maintains electrical neutrality within the half-cells and prevents the build-up of positive charges in the oxidation half-cell and negative charges in the reduction half-cell. Without the salt bridge, these charges would continue accumulating and eventually, the electrochemical reaction would stop.

Agar-agar is a jelly-like substance obtained from algae. It is used as a gelification agent in salt bridges in electrochemical cells.

Note: Agar-agar is not used in all types of salt bridges. They are only used in glass-tube salt bridges. Another type of salt bridge, called filter paper bridge, uses filter paper soaked in the inert electrolyte without the use of any jelly-like material.