electrochemical cells

• In a cell, a chemical reaction takes place at each electrode to convert chemical energy into electrical energy.
• Electrodes are usually a strip of metal but graphite can also be used.
• graphite is able to conduct electricity because it has one free electron which does not form a covalent bond
• An electrolyte is a solution which can conduct electricity because it contains ions.
• simple cell

  A) elcetrolyte

  B) electrode

  C) electrode

  D) wire

  E) voltmeter

  
• When different metals are placed in an electrolyte and connected together, voltage is produced.
• half-cells can be made using two half-cells. Each half-cell consists of a metal in a solution of its own ions.
• a copper/zinc cell

  A) zinc

  B) copper

  C) electrolyte

  D) copper sulfate

  E) zinc sulfate

  F) wire

  G) voltmeter

  
• half-cells are linked by an ion bridge (sometimes called a salt bridge). An ion bridge allows the movement of ions to complete the electrical circuit.
• A chemical reaction occurs at each electrode in the half-cell.
• Electrons flow in the wires from the species higher in the electrochemical series to the one lower in the electrochemical series.
• the electrochemical series is a series of metals arranged by the voltage they produce
• an oxidation reaction is the loss of electrons, opposite from how they appear on the electrochemical series
• a reduction reaction is a gain of electrons
• redox equations are reduction and oxidation reactions happening at the same time
• Electricity can be produced in cells where at least one of the half-cells does not involve metal atoms or ions
• This is required for cells involving the alkali metals as they are too reactive to be used as electrolytes
• Graphite makes a good electrode as it can allow the conduction of electricity but will not react with the electrolyte.
• The further apart elements are in the electrochemical series, the greater the voltage produced