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GALVANIC CELL
INTRODUCTION:
Galvanic cells are named for the Italian physicist and physician Luigi Galvani (1737–1798),
who observed that dissected frog leg muscles twitched when a small electric shock was applied,
demonstrating the electrical nature of nerve impulses
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DEFINATON:
It is an electrochemical cell that converts chemical energy into electrical energy and achieves
this by harnessing the energy produced by the redox reactions that occur within the cell
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The specie that losses its electrons
is said to be oxidized whereas the specie that gains the same electrons is said to be reduced
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The electrode which is positively charged is
called cathode and the electrode which is negatively charged is called anode
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The oxidation and reduction are
separated into compartments called half cells
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It maintains the electrical
neutrality within the circuit preventing the cell from rapidly running its reaction to equilibrium
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4- The external circuit is used to conduct the flow of electrons between the electrodes of the
cell and usually includes a load
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A light bulb is a example of a simple load where current (a flow of electrons) is used
to resistively heat a filament of metal, usually tungsten, until it radiates energy in the form of
visible light
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It involves a chemical reaction that makes the
electric energy available as the end result
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The cell uses two different metal electrodes, each in an electrolyte solution
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The metal of the anode will oxidize,
going from an oxidation state of 0 (in the solid form) to a positive oxidation state, and it will
become an ion
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This forms a solid metal that deposits on the
cathode
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This flow of electrons is an electrical current that can be used to do work, such as turn a motor
or power a light
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Also daniell cell is a special type of galvanic cell
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At the anode zinc is oxidized by the following half reaction
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7618 V )

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At the cathode zinc is reduced by the following reaction
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340 V )
Note that positively charged copper ions move towards the positive electrode, driven by a
reduction in chemical energy
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1018 V )

Figure:4
These processes result in the accumulation of solid copper at the cathode and the corrosion of
the zinc electrode into the solution as zinc cations ,weaker bonding (smaller magnitude of the
cohesive energy) in zinc compared to copper metal, which can be explained in terms of the
lack of bonding via partially filled d-orbitals in zinc
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The two
half cells each support one half of the reactions described above
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Excess electrons produced by the oxidation of zinc metal are
“pushed” out of the anode, which is therefore the negative electrode, travel through the wire

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and are "pulled" into the copper cathode where they are consumed by the reduction of copper
ions
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Since neither half reaction will occur independently of the other, the two half cells must be
connected in a way that will allow ions to move freely between them
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When the half cells are placed in two entirely different and separate containers, a salt bridge is
often used to connect the two cells
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In the above wet-cell during
discharge, nitrate anions in the salt bridge move into the zinc half-cell in order to balance the
increase in Zn2+ ions
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In the Daniell cell, the porous barrier cannot prevent the flow of copper ions into the zinc halfcell if it is driven by an applied voltage
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DESIGN:
In designing a cell To design a galvanic cell followings steps are taken:
Pick anodes and cathodes that maximize difference in reactivity
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To determine what voltage your anode and
cathode will produce
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The maximum voltage produced by your
galvanic cell will the sum of reactivity
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34V(Cu) + 0
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2) Pick a highly acidic electrolyte
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How close you get depends largely on how good your electrolyte is
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In general, strong acids are the best electrolytes
because, in general, they can pack the most ions
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Although the voltage of your cell is determined by the reactivity of the anode
and cathode, the current supplied by the cell is determined by the surface area of the anode and
cathode exposed to the electrolyte
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More ions mean more current
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However, cells have to be isolated
otherwise you will get a short between cells
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Figure:6
EFFICIENCY:
The maximum efficiency for an electrochemical cell is dependent on the oxidation-reduction
reaction that takes place
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G/ H = 1 - (T S)/ H

As soon as current begins to flow through a cell, energy is lost and efficiency is reduced
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We can think of resistance as being similar to
friction
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The galvanic cell produces
approximately 213 kJ per mole (65 g) of zinc
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