Chap 4 Electrochemistry

• Electrolysis


  The decomposition of an ionic compound when molten or in Aqua Solution by the passage of an electric current
• Electrolysis


  • Ionic compound should be either melted or in water so that they have free ions in order to allow electricity to pass through
• Electrode


  A conductor, often a metal or graphite Rod, that allows electric current to go in or out of an electrolyte
• Electrolyte


  The molten or aquous substance that undergoes electrolysis
• Molten


  Heated until it becomes a liquid
• Aquous


  Dissolved in water
• Cation


  A positively charged ion formed when an atom loses electrons
• Anion


  A negatively charged ion formed when an atom gains electrons
• Cathode


  The negative electrode that attracts positively charged cations
• Anode


  The positive electrode that attracts negatively charged anions
• Electrolysis


  1. Electric current flows through the circuit

  2. Electrons move from power supply to cathode making it negatively charged

  3. Anode becomes positively charged as it loses electrons

  4. Positive cations in electrolyte move towards cathode and gain electrons

  5. Negative anions in electrolyte move towards anode and lose electrons

  6. Electrons from anode move back towards power supply
• Oxidation


  Negative ions lose electrons at the anode
• Reduction


  Positive ions gain electrons at the cathode
• Binary molten ionic compound

  • Sodium chloride (Na+ and Cl-)
• Electrolysis of molten sodium chloride

  1. At anode: 2Cl- lose 2e- to form Cl2 gas

  2. At cathode: Na+ gain 1e- to form Na
• The electrode that is oxidized during the reaction is called the anode.
• The electrode that is reduced during the reaction is called the cathode.
• In a galvanic cell, electrons flow from the anode to the cathode through an external circuit.
• In electrolysis, the positive ions are reduced at the cathode while negative ions are oxidized at the anode.
• A half cell is one side of an electrochemical cell, consisting of an electrode and its solution.
• In an electrochemical cell, the positive terminal is called the anode (+) and the negative terminal is called the cathode (-).
• Redox reactions involve both reduction (gain of electrons) and oxidation (loss of electrons).
• Electron transfer occurs when two metals react with each other or with another substance.
• Oxidation involves losing electrons, while reduction involves gaining electrons.
• Redox reactions involve both oxidation and reduction occurring simultaneously.
• Oxidizing agents remove electrons from other substances, causing them to be oxidized.
• Reducing agents donate electrons to other substances, reducing them.
• During electrolysis, the products formed depend on the type of metal being extracted and the nature of the nonmetal involved.
• In an electrolytic cell, electrons are forced to flow from the cathode to the anode by an external power source.
• Redox reactions involve both reduction and oxidation occurring simultaneously.
• Electrolysis

  The process of using electricity to drive a chemical reaction
• Inert electrodes

  • They don't get involved in the chemical reactions, avoiding any interference
• Molten compounds

  Substances in a liquid state resulting from being heated above their melting points
• Molten compounds have

  Free ions that can carry charge during electrolysis
• Electrolysis of molten lead(II) bromide

  1. Connect electrodes to power supply

  2. Bromide ions travel to positive electrode (anode)

  3. Bromine gas forms at anode

  4. Lead ions travel to negative electrode (cathode)

  5. Lead metal forms at cathode
• Aqueous solution

  A substance mixed with water
• Ions in aqueous electrolyte

  • Cations from dissolved substance
  • Anions from dissolved substance
  • Hydrogen ions
  • Hydroxide ions
• Discharge at cathode

  • Metals or hydrogen are formed
• Discharge at anode

  • Non-metals other than hydrogen are formed
• Reactivity series

  A list of metals arranged in order of their reactivity, determines which metal ions get discharged at the cathode