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Electrochemistry

Lemon Battery Lemon battery Many fruits and liquids (fruit juices) can be used for the acidic electrolyte. Lemon battery is an electrochemical cell (Galvanic cell) constructed by using zinc and copper rods as electrodes. The juice inside the lemon acts as an electrolyte which conducts electricity. There are many variations of the lemon cell that use different fruits (or liquids) as electrolytes and metals other than zinc and copper as electrodes.
The EMF generated through a single lemon battery is enough to illuminate a light emitting diode (LED). A series of lemon batteries are used to operate a digital clock.

Learning Objectives

After completing the topic, the student will be able to:

  • Define electrochemistry and understand the principles behind the development of electrochemistry.
  • Distinguish electronic and electrolytic conductors.
  • State Ohm's law and apply Ohm's law to determine resistance, conductance, resistivity and conductivity.
  • Define and relate molar conductivity and equivalent conductivity.
  • Predict the effect of dilution on conductivity and classify the electrolytes based on conductivity.
  • Define electrolysis and explain the mechanism of electrolysis.
  • State Faraday's laws and use them for quantitative calculations in electrochemistry.
  • Know the processes involved in electroplating, electro–refining and electrolytic extraction of some elements.
  • Discuss the process of corrosion and give the methods to prevent corrosion.
  • Describe an electrochemical cell and distinguish electrolytic cell and galvanic cell.
  • Define standard potentials and use Nernst equation to calculate standard potentials.
  • Relate standard potentials and chemical reactivity of some metals and use electrochemical series to predict the products in some displacement reactions.
  • Describe the chemical reactions involved in dry cell battery, lead storage battery, cell phone battery and fuel cells and appreciate the use of fuel cells to prevent environmental pollution.
Thermal Power Plant Thermal power plant In a thermal power plant, heat is produced by burning coal or natural gas which is converted into mechanical energy and then into electrical energy. It needs a large area and several equipment. Pollution caused by it is a concern.
Electrochemistry

Electrochemistry, as the name suggests, is a branch of chemistry that combines chemical reactions that induce electrical effects and vice versa. In short, electrochemistry deals with electrical energy which interchanges with chemical energy. It involves either the use of an oxidation–reduction reaction to produce an electric current or the use of an electric current to produce an oxidation–reduction reaction.

The principle of electrochemistry is based on law of conservation of energy which states that energy can neither be created nor destroyed but it can be converted from one form to another form. As stated above, electrochemistry deals with the processes involving electrical energy and chemical energy inter-conversions. We know that power (electrical energy) is produced from solar power plants, thermal power plants, tidal plants, hydel plants, wind energy plants etc., where heat and mechanical energy are converted into electrical energy.

Electrical Batteries Electrical batteries Now–a–days rechargeable batteries (Electrochemical cells) are available. These electrochemical cells are pollution free when compared to thermal power plants.
Electrical energy from chemical energy

People are interested in chemical energy because we can produce electrical energy in laboratory. In the stated methods(solar power plants, thermal power plants, tidal plants, hydel plants, wind energy plants ) there is a need of large apparatus and assembly of instruments. But in case of chemical energy, small electrochemical cells are enough to produce energy.

The importance of Electrochemistry, in the history of discoveries in Physics and Chemistry, is immense, to say the least. Had it not been for the voltaic cell, where there was a controlled source of electrical charge, discoveries in electricity (and magnetism) would perhaps have been delayed. Many new metals and non–metals were isolated and collected solely because of electrolysis of compounds and solutions were possible with a voltaic cell.

The electrochemical energy conversions are used to produce long running storage batteries to use in automotive systems (refer to figure).

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