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Chemical reactions can release or absorb electrical energy. All electrochemical reactions are redox reactions. The transfer (flow) of electrons is electric current.
If the half reactions are physically separated the reaction can be turned into an electrochemical cell.
Activity Series
Activity Series
Some metals are more reactive (more easily oxidized). Metals higher on the table will oxide and the metals lower will be reduced.
Example
Example
When zinc metal is placed in copper sulfate the copper takes electrons from the zinc. As a result, the zinc will replace the copper in solution and the copper will become a solid deposit
Half reactions:
Zn(s) → Zn 2+(aq) + 2e-
Cu 2+(aq) + 2e- → Cu(s)
The solution becomes more clear as the copper ions are removed.
Electrochemical cells
Electrochemical cells
An electrochemical cell is any system that converts chemical energy into electrical energy.
Voltaic Cell
Voltaic Cell
a voltaic cells has two half-cells: one half with the reduction reaction and the other half with the oxidation reaction. The two half-cells are connected by a salt bridge, which transfers ions
The metals serve as electrodes. The anode is oxidized and the cathode is reduced.
Electrons are transferred by a wire between the electrodes. This is the electric current.
Common Voltaic cells
Common Voltaic cells
Dry cells
Dry cells
lead batteries
lead batteries
hydrogen fuel cells
hydrogen fuel cells
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