For a molten salt, the possible reactions are limited to those involving the ions from the
In aqueous situations, however, the possible reactions of water must also be included.
2H2O(l) + 2e H2(g) + 2OH(aq)
2H2O(l) O2(g) + 4H+(a
Because the oxidation and reduction potentials are opposites, we need to calculate only
one or the other. By convention, reduction potentials are calculated and are called
electrode potentials, E (with no subscript).
Electrode potentials are a measure of
The standard electrode potential, E, is the electrode potential when the
concentrations of solutes are 1 M, the gas pressures are 1 atm,
and the temperature has a specified value (usually 25C).
The superscript degree sign () signifies standardstate condit
Dependence of Cell Potential on Concentration: Nernst Equation
DG = DG + RT ln Q
Q is the thermodynamic equilibrium constant.
This equation allows us to relate E to E.
At 25C, this reduces to
Commercial Voltaic Cells
We next look at several commercial vol
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Duplication part of chromosome is copied
Inversion part of chromosome
Construction of Voltaic Cells
electrochemical cell, voltaic (galvanic cell), electrolytic cell, and halfcell.
the function of the salt bridge in a voltaic cell.
the reaction that occurs at the anode and the cathode in an
Stoichiometry of Electrolysis
In the 1830s, Michael Faraday showed that the total charge that flows in a circuit is
related to the amount of substance released at the electrodes.
One faraday of charge is the charge on one mole of electrons and is equal to
Predicting the Direction of Reaction
You can predict the direction of reaction by comparing the relative oxidizing (or
The stronger oxidizing agent will be reduced. (The stronger reducing agent will be
Will dichromate ion o
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In this solidstate battery, the electrodes are separated by a thin crystalline layer of
lithium iodide. Diffusion of the Li+ ion carries the current. The cell has high resistance
and, therefore, low voltage. It is very reliable and i