electrode potential

(noun)

The potential difference of a half-reaction that occurs across a reversible cell made up of any electrode and a standard hydrogen electrode.

Related Terms

Examples of electrode potential in the following topics:

  • Predicting Spontaneous Direction of a Redox Reaction

    • To figure this out, it is important to consider the standard electrode potential, which is a measure of the driving force behind a reaction.
    • The sign of the standard electrode potential indicates the direction in which the reaction must shift to reach equilibrium.
    • What happens to the standard electrode potential when the reaction is written in the reverse direction?
    • The magnitude of the potential must remain the same.
    • However, turning the equation around changes the sign of the standard electrode potential, and can therefore turn an unfavorable reaction into one that is spontaneous, or vice versa.

  • Free Energy and Cell Potential

    • Electricity is generated due to the electric potential difference between two electrodes.
    • In electrochemistry, the standard electrode potential, abbreviated E°, is the measure of the individual potential of a reversible electrode at standard state, which is with solutes at an effective concentration of 1 M, and gases at a pressure of 1 atm.
    • Since the standard electrode potentials are given in their ability to be reduced, the bigger the standard reduction potentials, the easier they are to be reduced; in other words, they are simply better oxidizing agents.
    • For example, F2 has a potential of 2.87 V and Li+ has a potential of -3.05 V.
    • In the example of Zn2+, whose standard reduction potential is -0.76 V, it can be oxidized by any other electrode whose standard reduction potential is greater than -0.76 V and can be reduced by any electrode with standard reduction potential less than -0.76 V.

  • Electrolytic Properties

    • In other systems, the electrode reactions can involve electrode metal as well as electrolyte ions.
    • In order to determine which species in solution will be oxidized and which will be reduced, the standard electrode potential of each species may be obtained from a table of standard reduction potentials, a small sampling of which is shown here:
    • Historically, oxidation potentials were tabulated and used in calculations, but the current standard is to only record the reduction potential in tables.
    • If a problem demands use of oxidation potential, it may be interpreted as the negative of the recorded reduction potential.
    • Positive potential is more favorable in this case.

  • Standard Reduction Potentials

    • Reduction potential (also known as redox potential, oxidation/reduction potential, or Eh) measures the tendency of a chemical species to acquire electrons and thereby be reduced.
    • Reduction potential is measured in volts (V) or millivolts (mV).
    • Each species has its own intrinsic reduction potential.
    • The standard reduction potential is defined relative to a standard hydrogen electrode (SHE) reference electrode, which is arbitrarily given a potential of 0.00 volts.
    • However, because these can also be referred to as "redox potentials," the terms "reduction potentials" and "oxidation potentials" are preferred by the IUPAC.

  • Principles of Electricity

    • Voltage and current are two important factors to consider in the study of neurons.Voltage, is the measure of potential energy generated by separated charge.
    • A voltage may represent either a source of energy (electromotive force), or it may represent lost or stored energy (potential drop).
    • In electrically active tissue, the potential difference between any two points can be measured by inserting an electrode at each point, and connecting both electrodes to to a specialized voltmeter.
    • Differences in concentration of ions on opposite sides of a cellular membrane lead to a voltage called the membrane potential.
    • These concentration gradients provide the potential energy to drive the formation of the membrane potential.

  • Van de Graff Generators

    • Using a moving belt, it can create extremely high potential differences.
    • Two electrodes are positioned near the bottom of the lower pulley and inside the sphere, over the upper pulley.
    • In this figure, a high, positive DC potential is applied to the upper roller.
    • Final potential is proportional to the size of the sphere and its distance from the ground.
    • Numbers in the diagram indicate: 1) hollow metal sphere; 2) upper electrode; 3) upper roller (for example an acrylic glass); 4) side of the belt with positive charges; 5) opposite side of the belt with negative charges; 6) lower roller (metal); 7) lower electrode (ground); 8) spherical device with negative charges, used to discharge the main sphere; 9) spark produced by the difference of potentials

  • Electrochemical Cell Notation

    • Recall that standard cell potentials can be calculated from potentials E0cell for both oxidation and reduction reactions.
    • A positive cell potential indicates that the reaction proceeds spontaneously in the direction in which the reaction is written.
    • Conversely, a reaction with a negative cell potential proceeds spontaneously in the reverse direction.
    • One beaker contains 0.15 M Cd(NO3)2 and a Cd metal electrode.
    • The other beaker contains 0.20 M AgNO3 and a Ag metal electrode.

  • 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.
    • The electrodes do not touch each other but are electrically connected by the electrolyte.
    • A battery stores electrical potential from the chemical reaction.
    • Electric potential is defined as the potential energy per unit charge (q).
    • The voltage, or potential difference, between two points is defined to be the change in potential energy of a charge q moved from point 1 to point 2, divided by the charge.

  • Other Rechargeable Batteries

    • NiMH batteries use positive electrodes of nickel oxyhydroxide (NiOOH), as does the NiCd, but the negative electrodes use a hydrogen-absorbing alloy instead of cadmium.
    • The lithium-ion battery is a family of rechargeable batteries in which lithium ions move from the negative electrode to the positive electrode during discharge, and back when charging.
    • The negative electrode of a conventional lithium-ion cell is made from carbon.
    • The positive electrode is a metal oxide, and the electrolyte is a lithium salt in an organic solvent.
    • The advantages of LiPo over the lithium-ion design include potentially lower cost of manufacture, adaptability to a wide variety of packaging shapes, reliability, and ruggedness.

  • Cathode Rays

    • If an evacuated glass tube is equipped with two electrodes and a voltage is applied, the glass opposite the negative electrode is observed to glow from electrons emitted from the cathode.
    • The early cold cathode vacuum tubes, called Crookes tubes, used a high electrical potential between the anode and the cathode to ionize the residual gas in the tube.
    • The voltage applied between the electrodes accelerates these low mass particles to high velocities.
    • In 1838, Michael Faraday passed a current through a rarefied air-filled glass tube and noticed a strange light arc with its beginning at the cathode (negative electrode) and its end almost at the anode (positive electrode).
    • Connect the two electrodes to a high voltage source and see them produce cathode rays.