Oxidation or Reduction a) Addition of oxygen to a substance b) 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) 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. DEFINITION OF KEYWORDS Electrolysis Splitting a substance using electricity Electrolyte Electrode Anode The substance being broken down. It is usually in form of molten or aqueous solution. It is a conductor through which electricity enters or leaves the electrolyte Positive electrode Cathode Negative electrode Anion Negative ion Cation Positive ion Examples of electrolytes Acids Nitric acid - HNO3 Sulphuric acid- H2SO4 Hydrochloric acid – HCl Bases/Alkali Sodium hydroxide - NaOH Potassium hydroxide - KOH Calcium hydroxide - Ca(OH)2 Salts : Potassium chloride – KCl Sodium Chloride - NaCl Potassium bromide - KBr MOVEMENT OF IONS Negative ion Positive ion Cathode Anode Electrolysis of Molten PbBr2 (lead(II)bromide) + CATHODE The lead ions move to the cathode and the bromide ions move to the anode. Pb2+ BrPb2+ - + ANODE Pb2+ Br- BrPb2+ - Br- = bromide ion At the cathode: Pb2+ gains electrons to form lead metal. Pb2+ + 2e- Pb It is REDUCED. = lead ion Cathode Anode At the anode: Br- loses electrons to form bromine gas. 2Br- Br2 + 2eIt is OXIDISED.