CHEM1003 Lecture Notes - Lecture 29: Cathodic Protection, Galvanic Corrosion, Stainless Steel
Lecture 29
Sunday, 22 May 2016
5:11 pm
Oxidation and Reduction (3)
Volatic Cells with Inert Electrodes:
• In situations where the reactants and products can't serve as the electrode
material, an inert electrode must be used
• Requirements
o Conducts electric current
o Neither oxidised or reduced in the cell
• E.g. graphite, platinum or gold
Example:
Electrochemical Cell Potentials:
• In standard ambient conditions (298 K, 1 mol/L) the voltage of this cell is 1.1V
• A cell reaction will be spontaneous (favourable) if the overall cell potential (E)
is positive
• Reaction potential (E) can be determined by using the potential of individual
half equations
o Standard reduction potentials for half equations have been measured to
a standard hydrogen electrode
o Measured under 'standard ambient conditions'
o Always written as a reduction potential
o Towards the top end - strongly oxidising agents
o Towards the bottom - strongly reducing agents
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
In situations where the reactants and products can"t serve as the electrode material, an inert electrode must be used: requirements, conducts electric current, neither oxidised or reduced in the cell, e. g. graphite, platinum or gold. Electrochemical cells: total voltage of a cell can be determined can be calculated using the formula, transfer of electrons will produce energy in the form of electricity if the reaction is spontaneous. If the eo cell is positive, the reaction is spontaneous. What does this mean: oxidation and reduction must occur together, this is because one substance has to release electrons, which have to be taken up by another substance, no absolute oxidising or reducing agent actually exists. In fact, the oxidising or reducing ability of a substance is a function of the reaction partner to be oxidised or reduced, respectively. Chemistry of corrosion/rust: drop of water acts as a micro-electrochemical cell.
