Chemical Reactiond

• Chemical Reaction


  A rearrangement of atoms in which some of the original bonds are broken and new bonds are formed to give different chemical structures
• In a chemical reaction, atoms are neither created, nor destroyed
• A chemical reaction is supported by Dalton's postulates
• Evidence of Chemical Change

  • Change of color
  • Formation of a solid
  • Formation of a gas
  • Emission of light
  • Release or absorption of heat
• Why use Chemical Equations

  • Shorthand way of describing a reaction
  • Provides information about the reaction
  • Formulas of reactants and products
  • States of reactants and products
  • Relative numbers of reactant and product molecules that are required
  • Can be used to determine amounts of the reactants and products
• Chemical Equation


  A shorthand expression for a chemical reaction
• Word equation


  • Aluminum combines with ferric oxide to form iron and aluminum oxide
• Chemical equation


  • Al + Fe2O3 → Fe + Al2O3
• Chemical Equations


  • Reactants are separated from products by an arrow
  • Coefficients are placed in front of substances to balance the equation
  • Subscripts
  • Reaction conditions are placed over the arrow
  • The physical state of the substances are indicated by the symbols (s), (l), (g), (aq)
• Types of Chemical Reactions

  • Synthesis or combination
  • Decomposition
  • Single replacement
  • Double replacement
  • Combustion
• Synthesis or Combination


  2 elements or compounds combine to form another compound
• Decomposition


  A compound breaks up to form 2 elements or simpler compound
• Single Replacement


  A more reactive element replaces a less reactive element in a compound
• Double Replacement


  Two compounds combine to form two new compounds, the cation from one compound replaces the cation in another compound
• Combustion


  A reaction that involves oxygen as a reactant and produces large amounts of heat
• Classify each of the reactions below

  • Mg + CuCl2 → MgCl2 + Cu (Single replacement)
  • CaCO3 → CaO + CO2 (Decomposition)
  • 2 HCl + Ca(OH)2 → CaCl2 + 2 H2O (Double replacement)
  • 4 Fe + 3 O2 → 2 Fe2O3 (Synthesis)
• Single Displacement


  The more reactive Zinc replaces the less reactive Copper