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CHEMICAL CHANGE

Electrolysis PowerPoint presentation

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CHEMICAL CHANGE

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  1. Electrolysis

  2. Oxidation or Reduction Addition of oxygen to a substance Loss of electrons c) Addition of hydrogen d) Decrease in oxidation number Use the equation below to Identify the chemical substance that that have undergone reduction / oxidation. Fe (s) + Ag+(aq)  Ag (s) + Fe2+`(aq)

  3. Learning Objectives • By the end of the lesson I will be able to: • 1) Describe the process of electrolysis. • 2) Explain how to separate lead(II)bromide using electrolysis.

  4. DEFINITION OF KEYWORDS Electrolysis Splitting a substance using electricity Electrode The substance being broken down. It is usually in form of molten or aqueous solution. Electrolyte It is a conductor through which electricity enters or leaves the electrolyte Anode Positive electrode Cathode Negative electrode Anion Negative ion Cation Positive ion

  5. Examples of electrolytes Salts : Potassium chloride – KCl Sodium Chloride - NaCl Potassium bromide - KBr • Acids • Nitric acid - HNO3 • Sulphuric acid- H2SO4 • Hydrochloric acid – HCl • Bases/Alkali • Sodium hydroxide - NaOH • Potassium hydroxide - KOH • Calcium hydroxide - Ca(OH)2

  6. Negative ion Positive ion MOVEMENT OF IONS Anode Cathode

  7. Electrolysis of Molten PbBr2(lead(II)bromide) - + CATHODE ANODE The lead ions move to the cathode and the bromide ions move to the anode. - + Pb2+ Br- Br- Br- Pb2+ Pb2+ Pb2+ Br-

  8. = bromide ion = lead ion At the cathode: Pb2+ gains electrons to form lead metal. Pb2+ + 2e- Pb It is REDUCED. At the anode: Br- loses electrons to form bromine gas. 2Br- Br2 + 2e- It is OXIDISED. Anode Cathode

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