chem chp 1

• Redox reaction


  A chemical reaction that involves the transfer of electrons between two chemical substances
• Redox reaction


  1. Electron transfer from one chemical substance to another

  2. Oxidation - the chemical substance that loses electrons

  3. Reduction - the chemical substance that gains electrons
• Oxidation and reduction


  Occur at the same time in a redox reaction
• Oxidation


  The process of losing electrons
• Reduction


  The process of gaining electrons
• Redox reactions can be explained in terms of transferring hydrogen or oxygen
• Magnesium and oxygen


  1. Magnesium loses electrons to become a positive ion (oxidation)

  2. Oxygen gains electrons to become a negative ion (reduction)
• Oxidation can be defined as the loss of hydrogen, loss of electrons, and gain of oxygen
• Reduction can be defined as the loss of oxygen, gain of hydrogen, and gain of electrons
• Half-ionic equations can be used to represent the oxidation and reduction processes in redox reactions
• Redox reaction


  A chemical reaction that involves the transfer of electrons between two chemical substances
• Oxidation


  The process where a substance loses electrons
• Reduction


  The process where a substance gains electrons
• Oxidation and reduction happen together in a redox reaction
• Agents


  Professionals who facilitate transactions, e.g. insurance agents, property agents
• Agents in chemistry


  • Oxidizing agents
  • Reducing agents
• Oxidizing agent


  Causes other substances to undergo oxidation, while itself undergoes reduction
• Reducing agent


  Causes other substances to undergo reduction, while itself undergoes oxidation
• Oxidizing agents have the fancy name "Hg67" and reducing agents have the name "Sm2"
• Common oxidizing agents


  • Dichromate (VI)

  Manganate (VII)

  Nitric acid

  Oxygen

  Halogens
• To be a good oxidizing agent, the substance must have high electronegativity, like the halogens
• Common reducing agents


  • Sulfur

  Metals

  Sulfur dioxide

  Hydrogen sulfide
• To be a good reducing agent, the substance must have high electron positivity, like metals
• Balancing dichromate (VI) reduction

  Write general equation

  Balance oxygen with water

  Balance hydrogen with H+ ions

  Balance number of atoms

  Balance charges by adding electrons
• Dichromate (VI) reduction


  Initial orange colour changes to green
• Acidified potassium dichromate (VI) solution

  K2Cr2O7, acidified to ensure complete reduction to Cr3+ ions
• Balancing manganate (VII) reduction

  Write general equation

  Balance oxygen with water

  Balance hydrogen with H+ ions

  Balance number of atoms

  Balance charges by adding electrons
• Manganate (VII) reduction


  Initial purple colour changes to colourless
• Potassium manganate (VII) solution

  KMnO4, neutral compound formed by adding K+ to cancel out MnO4- charge
• Balancing nitrate ion reduction

  Write general equation

  Balance oxygen with water

  Balance hydrogen with H+ ions

  Balance number of atoms

  Balance charges by adding electrons
• Nitrite ion reduction to nitrogen oxide is colourless-colourless