Electrochemical Cell Potential

Electrochemical Cells

• Electrochemical cell potential difference (emf) can be experimentally measured using a voltmeter: Ecell = E (cathode) – E (anode) = E (right) – E (left)
• Electrode potential of each half cell cannot be experimentally measured but can be calculated using the Nernst equation: Ox + ne- = Red

Classification of Electrochemical Methods

• There are three types of electrochemical methods:
  • Potentiometry
  • Conductimetry
  • Voltammetry

Potentiometry

• Measures the electrical potential developed by an electrode in an electrolyte solution at zero current flow, using the Nernst equation
• Nernst equation relates potential to concentration of analyte: E25°c = E° + (0.0591/n) log [Mn+]
• Potentiometric methods are based on measurements of the potential of electrochemical cells in the absence of appreciable currents (i.e. 0)

Conductimetry

• Measures the conductance of a solution, which depends on the concentration of its ions, using inert electrodes and alternating current

Electrochemistry

• Is the relationship between electrical properties and chemical reactions
• Electrical properties measured as: voltage, current, resistance
• Measurements are carried out by certain instruments, thus the methods are called instrumental methods

Electrochemical Cells

• Divided into two cells: Galvanic cell and Electrolytic cell
• Galvanic cell: Chemical energy is converted into electrical energy
• Electrolytic cell: Electrical energy is converted into chemical energy

Comparing Galvanic Cell and Electrolytic Cell

• Galvanic cell:
  • Generates current-potential
  • Chemical energy is converted into electrical energy
  • Spontaneous reaction to occur
  • Cathode is positive (+), Anode is negative (-)
• Electrolytic cell:
  • Consumes current-potential
  • Electrical energy is converted into chemical energy
  • Non-spontaneous reaction to occur
  • Cathode is negative (-), Anode is positive (+)

Electrodes

• Cathode: The electrode at which reduction occurs (gain of electrons), usually metal electrodes
• Anode: The electrode at which oxidation occurs (loss of electrons), usually metal electrodes

This quiz covers the measurement of electrochemical cell potential, including the use of voltmeter and Nernst equation. It also explains the calculation of electrode potential and the difference between cathode and anode.