Chemical reactions

• Chemical Reaction


  An indication for a chemical change and includes formation of new substances which have different chemical compositions from their original states
• Evidences for a Chemical Reaction

  • Change in color
  • Formation of gas
  • Formation of
  • Release or absorption of heat
• Chemical Equation


  Symbolic or shorthand way representing a chemical reaction and may be written as molecular/ionic equation
• Combination/Synthesis Reaction


  Reactants combine to form one product
• General Equation for Combination/Synthesis Reaction

  A+B C
• Decomposition/Analysis Reaction


  A compound is decomposed or broken down to its elemental composition
• General Equation for Decomposition/Analysis Reaction

  AB A + B
• Replacement/Substitution Reaction


  A substance replaces another substance; dependent on the relative activities of the elements which may involve replacement of metal in a compound by a more active metal
• General Equation for Replacement/Substitution Reaction

  ABC CB + A
• Double Decomposition Reaction


  Two compounds react to form new two compounds; positive ions exchange partners with negatives ions - usually precipitates or insoluble substances are formed
• Precipitate


  An insoluble substance that settles in a mixture. This is usually observed during chemical reactions upon mixing of two liquids.
• General Equation for Precipitate Formation

  AB + CD →AD + CB
• Neutralization Reactions


  Reaction between acid and base to form salt and water
• General Equation for Neutralization Reactions

  Acid + Base → Salt + H2O
• Combustion Reaction


  Hydrocarbons and CHO compounds yield CO2 and water when burned with O2
• General Equation for Combustion Reaction

  Carbon compounds + O2(g) → CO2(g) + H2O(g)