Module 11: ElectroChem

• Salt-bridge

  It isolates the reactants but maintains electrical contact between the two halves of the cell.
• What is the anode in an electrochemical cell?


  The electrode at which oxidation occurs.
• What is the cathode in an electrochemical cell?


  The electrode at which reduction occurs.
• What is the difference between a galvanic cell and an electrolytic cell?


  A galvanic cell spontaneously produces current, while an electrolytic cell requires an external source of energy.
• What is a half-cell reaction?


  An oxidation or reduction reaction occurring at an electrode.
• What is the Standard Hydrogen Electrode (SHE)?


  It consists of a platinum electrode coated with platinum black and hydrogen at 760 mm of mercury is passed over it.
• What does the electrode potential E measure?


  It measures the potential of an electrode relative to a standard, usually the SHE, and indicates the driving force of the electrode reaction.
• What is the theoretical cell potential?


  It is the algebraic sum of the individual electrode potentials of an electrochemical cell at zero current.
• What is liquid-junction potential?


  It is a potential developed across a boundary between electrolytes differing in concentration or chemical composition.
• What is Ohmic Drop (IR)?


  It is the amount of potential that is lost on the way from the reference electrode to the working electrodes.
• What is activation overpotential (overvoltage)?


  It is the additional potential required to cause some electrode reactions to proceed at an appreciable rate.
• What is concentration overpotential or concentration polarization?

  It is the additional voltage needed to carry out electrolysis in addition to the standard cell potential.
• What occurs in an oxidation/reduction reaction?


  Electrons are transferred from one reactant to another.
• What is oxidation in terms of electron transfer?

  Oxidation is the loss of electrons from an atom.
• What is reduction in terms of electron transfer?

  Reduction is the gain of electrons by an atom.
• What is the role of a salt bridge in an electrochemical cell?


  It maintains electrical contact while isolating the reactants.
• What are the types of electrochemical cells?

  • Galvanic cells: store electrical energy.
  • Electrolytic cells: consume electricity and require an external source of electrical energy for operation.
• What are the functions of indicator and reference electrodes in electrochemical measurements?


  • Indicator electrode: senses the presence or change in concentration of the oxidized and reduced forms of a redox couple.
  • Reference electrode: has a stable and well-known electrode potential.
• What are the characteristics of the Calomel and Silver-silver Chloride electrodes?


  • Calomel Electrode: Consists of mercury in contact with calomel and potassium chloride, with a porous frit for contact with the sample solution.
  • Silver-silver Chloride Electrode: Consists of a silver wire coated with silver chloride in contact with a potassium chloride solution, sealed with a porous plug.
• Standard Electrode Potential


  Electrode potential measured in solutions where all reactants and products are at unit activity. One way of measuring how easily a substance loses an electron
• Reducing agent


  electron donor
• Oxidizing agent


  electron acceptor