Electrochemistry

Cards (61)

  • Why do we add salt bridges?
    to complete the circuit
  • How does a salt bridge work?
    Allows the passage of ions to prevent the build up of charge
  • What is the electrochemical series?
    an order of the electrode potentials of substances based on their reducing power
  • When connecting a light bulb to a battery with half cells, why does the voltage eventually become 0?
    The concentration of solutions become the same
  • What is usually the main reason why a half cell is not producing its standard emf?
    The half cell is not under standard conditions
  • What are standard conditions for a half cell?
    1 mol/dm^3 of the solution to be reduced
    298K
    100KPa
  • What is electrochemistry?
    Electrochemistry is the branch of chemistry concerned with the interconversion of chemical and electrical energy.
  • What are the two basic types of electrochemical cells?
    The two basic types of electrochemical cells aregalvanic cells(also called voltaic cells) andelectrolytic cells.
  • What is the difference between a galvanic cell and an electrolytic cell?
    In a galvanic cell, a spontaneous chemical reaction generates an electric current.

    In an electrolytic cell, an electric current drives a nonspontaneous reaction.

    The two types are inverse processes.
  • What is an anode?
    An anode is the electrode at which oxidation takes place.
  • What is a cathode?
    A cathode is the electrode at which reduction takes place.
  • How did anode and cathodes get their names?
    Anions move TOWARD the anode.
    Cations move TOWARD the cathode.
  • What is the sign convention for anodes and cathodes?
    We regard the anode as negative and the cathode as positive.
  • Describe 4 qualities of an anode.
    Oxidation occurs at the anode.
    Electrons are "produced" in the anode.
    Anions migrate toward the anode.
    Anodes have negative sign.
  • Describe four qualities of a cathode.
    Reduction occurs at the cathode.
    Electrons are "consumed" in the cathode.
    Cations migrate toward the cathode.
    Cathodes have positive sign.
  • What are the conventions for galvanic shorthand notation?
    Anode half reaction on left, cathode half reaction on right.

    Single vertical line (|) indicates a phase boundary.

    Double vertical line (||) indicates the salt bridge.

    Anode is leftmost, cathode is rightmost.
  • What is a Daniell cell?
    A Daniell cell is a voltaic cell which uses a zinc anode and copper cathode. The ion solutions are zinc sulphate and copper (II) sulfate. The salt bridge is an arbitrary nonreactive salt.
  • How do columbs and volts relate to joules?
  • How does free energy relate to cell potential?
  • What is the value of Faraday's constant?
    F = 96,500 C / mol * e^-
  • What is a standard cell potential?
    The standard cell potential is the cell potential when...

    both the reactants and products are in their standard states

    solutes are at 1 M concentration

    gasses are at 1 atm

    Solids and liquids in pure form

    Specified temperature (usually 25' C)
  • What is the standard free-energy change?
  • How do the standard half-cell potentials contribute to the standard potential?
  • What is the
    Standard Hydrogen Electrode(S.H.E.)The standard hydrogen electrode is a reference half-cell which is used to obtain standard cellpotentials.
  • List the equations for this chapter
  • How does electrical potential depend on how much reaction occurs?
    An electrical potential doesnotdepend on how much reaction occurs.
  • How does spontaneity depend upon standard cell potentials?
    Positive standard cell potentials correspond to spontaneous reactions.
  • What is the Nernst Equation?
    The Nernst equation gives cell potential under nonstandard conditions. The Nernst equation is derived by taking the nonstandard Free Energy Change equation and substituting -nFE for free energy change and -nFE' for Standard Free energy change.
  • Describe the history of the Nernst Equation
    The Nernst Equation was named after Walther Nernst (1864-1941), the German Chemist who first derived it.
  • What is the base 10 Nernst Equation?
  • How does pH relate to cell potential at 25' C?
    A higher cell potential indicates a higher pH. Thus, we can measure the pH of a solution simply by measuring the Cell Potential.
  • How does a standard cell potential relate to its corresponding equillibrium constant?
    This relation is used to calculate equilibrium constants from standard cell potentials, especially when concentrations are very small and difficult to measure.
  • Name some applications of electrochemistry.
    1. Batteries
    2. Measure pH
    3. Calculate equilibrium constants when concentrations are small.
  • How far do Redox reactions typically progress?

    Almost all or almost none. There is little middle ground for redox reactions.

    A redox reaction will typically progress almost to completion or will hardly occur at all.
  • What are the three ways to determine equilibrium constants?
    1. From concentration data for solutions.
    2. From thermochemical data.
    3. From electrochemical data.
  • Name several types of commercial batteries
    Lead Storage Batteries
    Dry-Cell Batteries
    ------(Leclanche' cells)
    ------Alkaline dry-cell batteries (Longer life than leclanche)
    -----Mercury batteries (Very small)
    Nickel-Cadmium batteries (Rechargeable)
    Lithium batteries (Lightweight, rechargeable, high voltage)
    Fuel Cells
  • What is a Leclanche' cell battery?
    A Leclanche' cell battery is another name for a dry-cell battery.

    Leclanche cell batteries were patented by Frenchman George Leclanche' in 1866.
  • What is
    cathodic protection?Cathodic protection is the technique of protecting a metal from corrosion by connecting it to a second metal that is more easily oxidized.

    Example: galvanizing automobile steel (covering in a layer of zinc).
  • What is a
    sacrificial anode?A sacrificial anode is an easily oxidized metal in electrical contact with a less easily oxidized metal. For example, a magnesium stake in contact with a sample of iron. The magnesium will corrode, but the iron will not.
  • What is
    electrolysis?Electrolysis is the process of using an electric current to effect chemical change.