half-cell

(noun)

Either of the two parts of an electrochemical cell containing an electrode and an electrolyte.

Related Terms

  • voltaic cell
  • electrode
  • redox

Examples of half-cell in the following topics:

  • The Battery

    • One half-cell includes electrolyte and the anode, or negative electrode; the other half-cell includes electrolyte and the cathode, or positive electrode.
    • Some cells use two half-cells with different electrolytes.
    • A separator between half-cells allows ions to flow, but prevents mixing of the electrolytes.
    • Each half-cell has an electromotive force (or emf), determined by its ability to drive electric current from the interior to the exterior of the cell.
    • The net emf of the cell is the difference between the emfs of its half-cells, or the difference between the reduction potentials of the half-reactions.
  • Electrochemical Cell Notation

    • Cell notation is shorthand that expresses a certain reaction in an electrochemical cell.
    • The anode half-cell is described first; the cathode half-cell follows.
    • Within a given half-cell, the reactants are specified first and the products last.
    • A double vertical line ( || ) represents a salt bridge or porous membrane separating the individual half-cells.
    • A typical arrangement of half-cells linked to form a galvanic cell.
  • Voltaic Cells

    • A voltaic cell is a device that produces an electric current from energy released by a spontaneous redox reaction in two half-cells.
    • This redox reaction consists of two half-reactions.
    • In a typical voltaic cell, the redox pair is copper and zinc, represented in the following half-cell reactions:
    • Each half-cell is connected by a salt bridge, which allows for the free transport of ionic species between the two cells.
    • The cell consists of two half-cells connected via a salt bridge or permeable membrane.
  • Concentration of Cells

    • The standard potential of an electrochemical cell requires standard conditions for all of the reactants.
    • The change in Gibbs free energy for an electrochemical cell can be related to the cell potential.
    • The Nernst equation can be used to calculate the output voltage changes in a pair of half-cells under non-standard conditions.
    • Under standard conditions, the output of this pair of half-cells is well known.
    • Discuss the implications of the Nernst equation on the electrochemical potential of a cell
  • The Nernst Equation

    • In electrochemistry, the Nernst equation can be used to determine the reduction potential of an electrochemical cell.
    • In electrochemistry, the Nernst equation can be used, in conjunction with other information, to determine the reduction potential of a half-cell in an electrochemical cell.
    • Find the cell potential of a galvanic cell based on the following reduction half-reactions where [Ni2+] = 0.030 M and [Pb2+] = 0.300 M.
    • First, find the electromotive force for the standard cell, which assumes concentrations of 1 M.
    • The added half-reactions with the adjusted E0 cell are:
  • Free Energy and Cell Potential

    • The basis for an electrochemical cell, such as the galvanic cell, is always a redox reaction that can be broken down into two half-reactions: oxidation occurs at the anode, where there is a loss of electrons, and reduction occurs at the cathode, where there is a gain of electrons.
    • If E°cell > 0, then the process is spontaneous (galvanic cell)
    • If E°cell < 0, then the process is non-spontaneous (the voltage must be supplied, as in an electrolytic cell)
    • A demonstration electrochemical cell setup resembling the Daniell cell.
    • The two half-cells are linked by a salt bridge carrying ions between them.
  • Gap Junctions

    • A gap junction is a specialized cell junction that directly connects the cytoplasm of two cells.
    • Each gap junction channel is made up of two half channels (hemichannels), one in each cell’s membrane. 
    • These half channels join together, bridge the extracellular space in the process, and form the entire channel that spans both cell membranes. 
    • Each of these half channels is called a connexon. 
    • For instance, when heart cells need to beat in unison, gap junctions allow for the transmission of electrical signals between the cells. 
  • Exocytosis

    • Exocytosis is the process by which cells release particles from within the cell into the extracellular space.
    • Exocytosis is used continuously by plant and animal cells to excrete waste from the cells.
    • The next stage that occurs is vesicle tethering, which links the vesicle to the cell membrane by biological material at half the diameter of a vesicle.
    • In some cells, there is no priming.
    • The contents are then released to the exterior of the cell.
  • Dry Cell Battery

    • The dry cell is one of many general types of electrochemical cells.
    • Unlike a wet cell, a dry cell can operate in any orientation without spilling, as it contains no free liquid.
    • A common dry-cell battery is the zinc-carbon battery, which uses a cell that is sometimes called the Leclanché cell.
    • The paste of ammonium chloride reacts according to the following half-reaction:
    • An illustration of a zinc-carbon dry cell.
  • Tumor Suppressor Genes

    • Tumor-suppressor genes keep regulatory mechanisms of cell division under control and prevent abnormal cell growth.
    • Like proto-oncogenes, many of the negative cell cycle regulatory proteins were discovered in cells that had become cancerous.
    • Mutated p53 genes have been identified in more than one-half of all human tumor cells.
    • At this point, a functional p53 will deem the cell unsalvageable and trigger programmed cell death (apoptosis).
    • Cells such as these daughter cells quickly accumulate both oncogenes and non-functional tumor suppressor genes.
Subjects
  • Accounting
  • Algebra
  • Art History
  • Biology
  • Business
  • Calculus
  • Chemistry
  • Communications
  • Economics
  • Finance
  • Management
  • Marketing
  • Microbiology
  • Physics
  • Physiology
  • Political Science
  • Psychology
  • Sociology
  • Statistics
  • U.S. History
  • World History
  • Writing

Except where noted, content and user contributions on this site are licensed under CC BY-SA 4.0 with attribution required.