Chemical+effects+of+electric+current

=Chemical effects of electric current= When electric current is passed through a conducting solution, some chemical reaction takes place.  Example: - (a) When electric current is passed through water, water dissociates into hydrogen and oxygen. Hydrogen is deposited over negative pole and oxygen is deposited over positive pole. Deposition of hydrogen and oxygen at different poles is visible in the form of bubbles. (b) When electric current is passed through the solution of a metal salt, such as solution of copper sulphate, metal gets deposited at the negative pole, because metal is positively charged. (c) Sometimes, the colour of solution also changes when electric current passes through it. The above examples are some of the chemical effects of electric current. The chemical reaction depends upon the type of solution through which electric current is passed. Electrolysis:  Electrolysis, the process of decomposing a solution or a molten compound by passing an electric current through it. Electrolysis is used in refining gold, silver, copper, and tin, and for obtaining aluminum, sodium, magnesium, and other metals from their ores. Electroplating is the use of electrolysis to coat a metallic object with a thin layer of another metal. Anodizing is the use of electrolysis to coat a metallic object with a thin layer of oxide for protection against corrosion and wear. Electrolysis is also used for the production of oxygen, hydrogen, chlorine, caustic soda, and other substances.

Electrolysis is carried out in an electrolytic cell. In the cell, the electrolytic solution or molten electrolyte is in contact with two solid conductors called electrodes. The electrodes are connected to opposite poles of a battery. The electrode connected to the positive pole is called the anode and the electrode connected to the negative pole is the cathode.

Substances that undergo electrolysis are either solutions of electrolytes or electrolytes that have been melted. When dissolved or molten, electrolytes separate into ions, atoms or groups of atoms that bear an electrical charge from having lost or gained one or more electrons. During electrolysis, ions with a positive electrical charge move toward the cathode, where they take up electrons; ions with a negative charge move toward the anode, where they give up electrons. This transfer of electrons causes chemical changes to take place at each electrode. 

**Electrolysis of water**
Pure water is a poor conductor of electricity. However, when few drops of H2SO4 are added to water, it becomes an electrolyte. **H2O(l)** → **H+(aq) + OH-(aq)** At cathode **4H+(aq) + 4e-** → **2H2(g)** At anode **4OH-(aq) - 4e-** → **2H2O(l) + O2(g)**

<span style="background-color: #ffffff; color: #333333; font-family: arial,helvetica,clean,sans-serif;"> Faraday's laws of electrolysis state: 1. The amount of chemical change that takes place in a solution during electrolysis is proportional to the amount of current passed through the solution. 2. The amount of a substance that is deposited is proportional to its equivalent weight (its atomic weight divided by its valence).

<span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; font-size: small; text-align: justify;">media type="custom" key="25480374" media type="custom" key="25556084" <span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; font-size: small; text-align: justify;">Electrolysis of Sodium Hydroxide solution: <span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; font-size: small; text-align: justify;">media type="custom" key="25482016"

Sites for simulation:
http://group.chem.iastate.edu/Greenbowe/sections/projectfolder/flashfiles/electroChem/electrolysis10.html metal electrodes http://www.sepuplhs.org/high/hydrogen/electrolysis_sim.html - electrolysis of water

<span style="background-color: #ffffff; color: #0066cc; display: block; font-family: Arial,Helvetica,sans-serif; font-size: small; text-align: justify;">Electroplating: <span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; font-size: small; text-align: justify;">Electroplating is one of the chemical effects of electric current. Electroplating is a chemical process using which a metal is coated with a layer of another desired metal. Electroplating is done to make the metals shiny. Electroplating is done over the articles made of iron to make the iron shiny and to prevent iron from getting rusted. <span style="background-color: #ffffff; color: #0066cc; display: block; font-family: Arial,Helvetica,sans-serif; font-size: small; text-align: justify;">Example <span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; font-size: small; text-align: justify;">Wheel rims, handle of cycle, etc. are made shiny by the method of electroplating. <span style="background-color: #ffffff; color: #0066cc; display: block; font-family: Arial,Helvetica,sans-serif; font-size: small; text-align: justify;">Process of electroplating: <span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; font-size: small; text-align: justify;">In the process of electroplating, metal salt solution is taken in a container. Salt of metal is chosen which is to be coated over another metal. Metal which is to be coated is dipped in the solution and connected with negative pole. Metal for desired coating is connected with positive pole.

<span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; font-size: small; text-align: justify;">When electric current is passed through the solution, metal from anode is dissolved in the salt solution and deposited over the negative pole (cathode). Thus, coating of desired metal is obtained on another metal. <span style="background-color: #ffffff; color: #0066cc; display: block; font-family: Arial,Helvetica,sans-serif; font-size: small; text-align: justify;">Use of electroplating: <span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; font-size: small; text-align: justify;">(a) Water pipes, which are made of iron, are coated with a layer of zinc metal by the process of electroplating. Zinc is less reactive than iron and thus prevents the iron pipe from getting rusted. <span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; font-size: small; text-align: justify;">(b) Rims of wheel of cycle, cars, etc. are electroplated with chromium metal. Layer of chromium metal give them shiny appearance and prevents from rust. <span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; font-size: small; text-align: justify;">(c) Ornaments made of silver or other cheap metals are electroplated with gold to give them appearance like gold. <span style="background-color: #ffffff; display: block; font-family: Arial,Helvetica,sans-serif; font-size: small; text-align: justify;">(d) Tin cans used for storing food are made of iron electroplating with a coat of tin. Tin is less reactive than iron, and prevent foods packed in them from getting spoiled. media type="custom" key="25611974" media type="custom" key="25611994"

Bibliography: http://www.excellup.com/ClassEight/scienceight/electrochemistryeight.aspx http://science.howstuffworks.com/electrolysis-info.htm http://chemistry.tutorvista.com/physical-chemistry/electrolysis.html