Understanding Electrolysis: Process, Reactions, and Examples, Lecture notes of Chemical Principles

Download Understanding Electrolysis: Process, Reactions, and Examples and more Lecture notes Chemical Principles in PDF only on Docsity! =lectro ysis Electrolysis Electrolysis “Ionic substances in solution or in a melt can be electrolysed.This is because they contain free moving ions.” What type of compounds can be electrolysed? Electrolysis of molten zinc chloride: zinc chloride  zinc + chlorine ZnCl2(l)  Zn(l) + Cl2(g) Lets look at an example Explanation: + - Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- positive electrode (anode) negative electrode (cathode) molten zinc chloride (ions free to move) Zn2+Zn2+ Zn2+ Zn2+ Zn2+ Zn2+ Zn2+ Cl- At the electrodes… The ions in the molten liquid become atoms by either gaining or losing electrons. At the CATHODE (-) Zinc ions each gain 2 electrons from the cathode (the electrons are pumped round the circuit from the powerpack) Zn2+ + 2 e-  Zn Silvery liquid White solid that melts to form dull white liquid At the CATHODE (-) Zn2+ + 2 e-  Zn This GAIN of electrons by the zinc ion is called REDUCTION This LOSS of electrons by chloride is called OXIDATION 2Cl-  Cl2 + 2e- Anode (+) Cathode (-) Always non-metals Always oxidation (LOSS of Electrons) Usually a gas Always metals or hydrogen Always reduction (GAIN of electrons) Sometimes a solid (metal), sometimes bubbles (H2) Some examples for you to try 1. Copper (II) Chloride 2. Nickel (II) Bromide 3. Zinc (II) Iodide Predict the product at each electrode and write the half-equations for each. Answers 1. Copper (II) Chloride Anode - Chlorine gas Cl2 Answers 1. Copper (II) Chloride Anode - Chlorine gas Cl2 2 Cl-  Cl2 + 2e- Answers 1. Copper (II) Chloride Anode - Chlorine gas Cl2 2 Cl-  Cl2 + 2e- Cathode Answers 1. Copper (II) Chloride Anode - Chlorine gas Cl2 2 Cl-  Cl2 + 2e- Cathode – Copper metal Cu Cu2+ + 2e-  Cu Answers 1. Copper (II) Chloride Anode - Chlorine gas Cl2 2 Cl-  Cl2 + 2e- Cathode – Copper metal Cu Cu2+ + 2e-  Cu Answers 2. Nickel (II) Bromide Anode - Answers 2. Nickel (II) Bromide Anode - Bromine Br2 2 Br-  Br2 + 2e- Cathode – Answers 2. Nickel (II) Bromide Anode - Bromine Br2 2 Br-  Br2 + 2e- Cathode – Nickel metal Ni Answers 2. Nickel (II) Bromide Anode - Bromine Br2 2 Br-  Br2 + 2e- Cathode – Nickel metal Ni Ni2+ + 2e-  Ni Answers 3. Zinc (II) Iodide Anode - Answers 3. Zinc (II) Iodide Anode - Iodine I2 Answers 3. Zinc (II) Iodide Anode - Iodine I2 2I-  I2 + 2e- Answers 3. Zinc (II) Iodide Anode - Iodine I2 2I-  I2 + 2e- Cathode – Zinc metal Zn Zn2+ + 2e-  Zn Answers 3. Zinc (II) Iodide Anode - Iodine I2 2I-  I2 + 2e- Cathode – Zinc metal Zn Zn2+ + 2e-  Zn Answers 3. Zinc (II) Iodide Anode - Iodine I2 2I-  I2 + 2e- Cathode – Zinc metal Zn Zn2+ + 2e-  Zn