Cathode

Definition

A cathode is an electrode where reduction occurs during an electrochemical reaction, attracting cations from the solution. This term is central to understanding how electrochemical cells function, as it is one of the two key electrodes, the other being the anode. The cathode plays a crucial role in various analytical techniques by facilitating the transfer of electrons and enabling chemical transformations essential for measurements and analysis.

5 Must Know Facts For Your Next Test

1. In a galvanic cell, the cathode is typically the positive electrode, while in an electrolytic cell, it is the negative electrode due to the applied voltage.
2. The reduction potential of the cathode determines how easily a substance will gain electrons during a reaction, which is vital for predicting the outcome of electrochemical processes.
3. Different materials can be used as cathodes, including metals like platinum and graphite, which can influence the efficiency and effectiveness of the electrochemical reaction.
4. In coulometry and electrogravimetry, measuring the current at the cathode allows for precise quantification of analytes based on Faraday's laws of electrolysis.
5. The cathode's surface properties, such as roughness and area, can impact reaction rates and overall performance in electrochemical applications.

Review Questions

• How does the role of the cathode differ between galvanic and electrolytic cells?
  • In galvanic cells, the cathode is where reduction occurs and it acts as the positive electrode. This means it attracts cations from the electrolyte and facilitates electron gain, leading to energy production. Conversely, in electrolytic cells, the cathode is where reduction still happens but it becomes the negative electrode because an external voltage is applied to drive non-spontaneous reactions. Understanding this difference is key to comprehending how electrochemical cells operate.
• Discuss how the choice of material for the cathode affects electrochemical reactions in analytical techniques.
  • The choice of material for the cathode significantly influences electrochemical reactions in techniques like coulometry and electrogravimetry. Different materials exhibit varying levels of conductivity and catalytic activity, which can alter reaction rates and efficiencies. For instance, a platinum cathode might provide a more stable and efficient platform for certain reductions compared to a less conductive material. This choice impacts not only sensitivity but also accuracy in quantitative analyses.
• Evaluate the importance of surface properties of the cathode in enhancing electrochemical performance during analysis.
  • The surface properties of the cathode play a crucial role in enhancing electrochemical performance. Characteristics such as surface roughness and active site availability can facilitate greater electron transfer rates and influence reaction kinetics. A well-optimized surface can lead to improved sensitivity and quicker response times in analytical applications. This becomes vital when working with low concentration analytes or during rapid analysis scenarios, making surface modification techniques a critical area of research.

Related terms

Anode: The electrode where oxidation occurs during an electrochemical reaction, releasing electrons into the external circuit.

Electrolyte: A substance that produces an electrically conducting solution when dissolved in a solvent, allowing ions to move between electrodes.

Redox Reaction: A chemical reaction involving the transfer of electrons between two species, consisting of oxidation (loss of electrons) and reduction (gain of electrons).