Classification of Chemical Reactions

• Redox reactions


  Reactions involving the transfer of electrons
• Unit 12 Learning Goals


  • Identify redox reactions and differentiate between the different types of redox reactions
  • Identify which halogens or metals are more reactive and will produce a reaction
  • Predict products of simple reactions
  • Identify when oxidation or reduction has occurred
  • Identify changes in oxidation numbers
  • Write balanced half reactions or redox reactions
• Chemical changes result in a different chemical compound/nature after a reaction
• A chemical change could be a new compound forming or the loss/gain of electrons from a compound
• Chemical changes can only be reversed with another chemical reaction
• The signs of a chemical reaction occurring are changes in color, smell, energy, production of a gas or precipitate, and changes in energy potential
• When a chemical reaction occurs, the mass of the reactants is perfectly equal to the mass of the products
• Mass is not created or destroyed
• Atoms are rearranged (or electrons lost/gained), but matter is not appearing or disappearing
• The new chemical products may have different physical and chemical properties
• Writing Balanced Chemical Equations

  1. The left side is the "reactant side" and the right side is the "product side"

  2. Make a table and count the number of atoms on the reactant vs product side of the reaction to balance the chemical equation
• NAD+


  Electron carrier, oxidizing agent, accepts electrons
• NADH


  Reducing agent, donates electrons
• NADH carries electrons to the electron transport chain
• Redox reactions involving NAD+ allow for maximum energy to be obtained from the combustion of glucose in our cells
• Without redox reactions involved in glucose breakdown, the energy we would harness would be close to the amount of energy needed to digest it (no net positive intake of energy)
• Types of Redox Reactions


  • Decomposition reactions
  • Synthesis reactions
  • Combustion reactions
  • Single displacement/replacement reactions
• Decomposition Reactions


  Molecule breaking into smaller molecules/pure elements
• Decomposition Reactions


  General format: AB → A + B
• Synthesis Reactions


  Synthesis of a molecule from its constituent elements or linking molecules into a more complex molecule
• Combustion Reactions


  Any molecule that contains carbon and hydrogen burning in the presence of oxygen gas to make carbon dioxide and water vapor
• Combustion Reactions


  General format: CxHy + O2 → CO2 + H2O
• Single Displacement Reactions


  One more "reactive" metal replacing another, or a more "reactive" halogen replacing another
• Single Displacement Reactions


  General format: AB + C → AC + B
• All redox reactions are single displacement reactions
• What drives single replacement reactions?


  An atom can replace another if it is considered more reactive on the reactivity series
• Potassium can replace calcium in a compound, but zinc cannot replace lithium in a compound
• Nonmetal Reactivity


  Fluorine can replace any other nonmetal as it is more reactive, but iodine cannot replace fluorine in a compound
• Predicting Products


  1. Anticipate whether a reaction will occur based on the activity series

  2. The reaction will not occur if the activity series predicts the element cannot replace the other
• Predicting Products


  • MgCl2 + 2Li → 2LiCl + Mg (reaction occurs as lithium is more reactive)
  • Fe(NO3)3 + Pb → No reaction as lead is less reactive than iron
• Oxidation


  Loss of electrons, increase in oxidation number
• Reduction


  Gain of electrons, decrease in oxidation number
• A redox reaction is an oxidation reduction reaction in which electrons are transferred
• If atoms change their oxidation number during a reaction, the reaction is a redox reaction
• If oxidation has occurred, reduction has also simultaneously occurred
• The apparent charge assigned to an atom of an element as if all bonds were ionic bonds is called the oxidation number</b>
• Oxidation numbers may be +, -, or 0, and are not the same as ionic charges
• All pure elements have an oxidation number of 0
• Monatomic ions have the charge of the ion as their oxidation number
• Oxygen is -2 and Hydrogen is -1 in compounds, except for some exceptions