Transcript Electrochemical Cells - Salisbury Composite High School

Voltaic Cells
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Components of a Voltaic cell
• consists of an electric cell that is made by placing
conductors (electrodes) in conducting solutions
(electrolytes)
• A cell contains 2 half cells each with an
electrode and electrolyte
Positive electrode – cathode
Negative electrode – anode
Electrons move from anode to cathode
This movement is called electricity
Components of a Voltaic cell
• Connecting wire – makes the external
circuit
• Salt bridge or porous barrier – connects
the two solutions without allowing
mixing so that ions can move freely
• Chemtoons
• YouTube - Chemistry Music Video:
Electrochemistry (You Start At The Anode)
Anode
Cathode
Negative electrode
Positive electrode
Electrons leave through the wire
Electrons enter through the wire
Reducing agent is oxidized
Oxidizing agent is reduced
Positive charge is produced in
the electrolyte
Positive charge is removed from the
electrolyte
Anions drift toward anode
Cations drift toward the cathode
Cations move away
Anions move away
• As negative electrical charges (electrons) are carried
away from the anode to the cathode through the
external circuit, a current is produced. Ions moving
through the porous barrier maintain electrical
neutrality in the solutions.
• voltaicCell
Cell Notation
Anode(-) / electrolyte // electrolyte / Cathode (+)
Cell Potential
• The difference in electrical potential energy
between the anode and the cathode in the cell (v)
▫ Depends on the relative tendency of the reactants in
the cell to lose and gain electrons
▫ Independent of the size of the cell
• standard cell: all entities in the half reactions
are at SATP and at concentration of 1.0 mol/L
• standard cell potential (Eo): the maximum
electric potential difference of a standard cell.
Difference per unit charge between the anode
and the cathode.
• standard reduction potential (Ero) is a
relative measure of the tendency of an oxidizing
agent to gain electrons (undergo reduction).
The value may be reversed to obtain oxidation
potentials. See redox table.
• Values for the reduction potentials are
assigned using hydrogen half cell as the
reference half cell.
▫ 2H+(aq) + 2e-  H2(g) Ero = 0.00 V
▫ This half cell has been arbitrarily assigned a value
of zero.
▫ Reactions above are +, stronger oxidizing agents
▫ Reactions below are -, and are stronger reducing
agents
• The standard cell potential is the sum of oxidation
and reduction potentials in a cell
• Eo = Ero – Ero
or Eo = Eredo + Eoxo
▫ If Eo is positive  spontaneous reaction
▫ If Eo is negative  non spontaneous reaction
Galvanic Cell with Zinc and Copper (You-tube)
Galvanic Cell with Zinc and Copper