Redox Reactions - SS1 Chemistry Past Questions and Answers - page 4

An electrochemical cell is a device that converts chemical energy into electrical energy through redox reactions. It consists of two half-cells, an anode and a cathode, connected by an external circuit and an electrolyte solution. The anode is the site of oxidation, where a species loses electrons, while the cathode is the site of reduction, where a species gains electrons.

When an electrochemical cell operates, oxidation occurs at the anode, releasing electrons into the external circuit. The electrons flow through the external circuit from the anode to the cathode, generating an electric current. Meanwhile, reduction takes place at the cathode, where the electrons combine with species from the electrolyte or an external source. This flow of electrons maintains the charge balance and enables the cell to sustain the redox reactions.

Within the cell, the electrolyte solution serves as a medium for ion migration between the two half-cells, ensuring charge neutrality. It contains ions that can participate in the redox reactions, facilitating the transfer of charge and maintaining the flow of current. The anode and cathode are often made of different materials to create a potential difference or voltage between them, enabling the generation of electrical energy.

Electrochemical cells have a wide range of applications in various aspects of everyday life and industries due to their ability to convert chemical energy into electrical energy. Here are some notable applications:

1. Batteries: Batteries are perhaps the most common application of electrochemical cells. They power portable devices such as smartphones, laptops, and electric vehicles. For example, lithium-ion batteries utilise redox reactions between lithium ions and transition metal compounds to store and release electrical energy. The oxidation and reduction reactions occur at the anode and cathode of the battery, respectively, allowing the flow of electrons and generating a potential difference.
2. Fuel cells: Fuel cells are electrochemical devices that generate electricity by utilising the direct conversion of the chemical energy of a fuel (e.g., hydrogen, methanol) into electrical energy. They find applications in stationary power generation, transportation, and even space exploration. For instance, hydrogen fuel cells combine hydrogen and oxygen to produce water, releasing electrons in the process. These electrons flow through an external circuit, producing electrical energy.
3. Corrosion protection: Electrochemical cells play a vital role in preventing corrosion in metal structures and equipment. By employing sacrificial anodes, such as zinc or magnesium, the anode material undergoes oxidation instead of the protected metal. This sacrificial corrosion mechanism protects the metal from oxidation and ensures its longevity.
4. Electroplating: Electroplating is a process used to coat one metal with a layer of another metal. It finds applications in decorative purposes, corrosion resistance, and electronic components. Electroplating relies on the principles of electrochemical cells, where the metal to be plated acts as the cathode, attracting cations of the plating metal from the electrolyte solution. Redox reactions occur at the anode and cathode, depositing the desired metal onto the surface of the object.
5. Sensors and biosensors: Electrochemical cells are utilised in sensors and biosensors to detect and measure various chemical substances and biological analytes. These devices use redox reactions to convert the analyte concentration into an electrical signal. For example glucose biosensors employ enzymes that catalyse the oxidation of glucose, generating an electric current proportional to the glucose concentration.