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Electrochemistry is converting chemical energy to electrical energy and vice versa. It is primarily concerned with the generation of electricity from the energy released during spontaneous reactions and the use of electrical energy for non-spontaneous chemical changes.
Electrochemical reactions are less polluting and more energy-efficient than traditional reactions. A salt bridge is one type of device that can be used to create an electrochemical cell. There are two types of salt bridges: filter paper bridges and glass tube bridges. The article below concerns the glass tube bridge definition and its use in the zinc copper galvanic cell.
Salt Bridges: What Are They?
The salt bridge is a device used in laboratories that connects the reduction and oxidation of half-cell components of a voltaic cell. A voltaic cell is a form of an electrochemical cell.
Primarily, a salt bridge is divided into two types, namely,
- Filter paper bridge
- Glass tube bridge.
This article will discuss the glass tube bridge in detail.
Glass Tube Bridge
According to the glass tube bridge definition, it is a device in the shape of a U, connecting the reduction and oxidation half-cell constituents of a galvanic or electrochemical cell.
Usually, this salt bridge contains a mixture of chloride, potassium, nitrate, and ammonium ions. The materials utilised to fill the gaps were chosen for their inertness to the cell’s chemical components. For creating a proper glass tube salt bridge, relative molecular weight and migratory speed are also considered. For gelification, agar is used in a glass tube salt bridge.
The conductivity of a glass tube bridge rises with the electrolyte solution’s concentration, but only to a certain extent. The rise in the concentration of the electrolyte solution causes a reduction in conductivity after a certain point. Since the conductivity of a salt bridge is directly related to its width, wider salt bridges are generally better conductors.
How To Prepare a Glass Tube Bridge?
A glass tube bridge is made by heating and bending a glass tube into the shape of a U. The tube is then filled with agar-agar and bridge materials. The bridge materials can either be potassium chloride or sodium sulphate. The electrolyte is frequently held in agar-agar since a salt solution might easily permeate the cell. The glass tube bridge’s length is customisable depending on the equipment, but its width is typically 0.86mm.
Working on a Glass Tube Bridge
Let’s take a look at an example of a salt bridge in a zinc copper galvanic cell to understand its mechanism in more detail.
Zinc and copper metal pieces are dipped in salt solutions with high concentrations of their respective salts in a conventional galvanic cell. Assume we put 1 mol of copper sulphate (CuSO₄) and 1 mol of zinc sulphate (ZnSO₄) in two separate beakers. We’re left with [Cu+2][SO4-2] and [Zn+2][SO4-2] when these two salts are totally dissolved.
When these two solutions are linked, oxidation and reduction reactions are triggered based on the electrode potential. In the zinc-copper cells, the resultant voltage is determined to be 1.10 V.
What happens at the anode?
By supplying 2 electrons to the cathode side, the zinc metal on the anode side oxidised to form zinc ions. This is owing to zinc’s lower electrode potential. As a result, as the reaction progresses, more zinc ions are generated, causing the solution to become increasingly positively charged.
What happens at the cathode?
Copper ions reduce to copper metals on the cathode side, gaining electrons from the anode side. As the reaction develops, it leaves [SO4-2] in the solution, which becomes increasingly negative.
Requirement of the glass tube bridge in the process
As time passes, the charged species build on the electrodes based on their electrode potential. The electrochemical cells are unable to continue running due to the overcharged electrode system, and they eventually shut down. As a result, the glass tube salt bridge is employed in electrochemical cells. According to the glass tube bridge definition, the device connects both half cell components of the cell, retaining the electrical neutrality of the internal circuit. The 2 half cells would have been charged, thereby stopping the charge flow entirely, if it weren’t for the glass tube salt bridge.
Conclusion
The majority of electrochemical cells are composed of 2 halves. The half-cells divide the reaction’s oxidation and reduction halves, allowing current to pass through an external wire. As per the glass tube bridge definition, it maintains a neutral charge in each cell and prevents the cell from quickly reaching equilibrium. So, upon adding a glass tube salt bridge, the circuit is created, and the current can flow. The anions travel toward the anode in the salt bridge, whereas the cations move towards the cathode.
