Chemical Reactions and Its Types

• Chemical Reaction


  Transformation of substance(s) into one or more new substances
• Chemical Change


  Specific process of chemical reaction involving reactants and products
• Reactants


  Starting materials used up to form new substances
• Products


  Final, new materials formed after a chemical reaction
• Chemical Equation


  Method to symbolically represent any chemical reaction using chemical symbols, subscripts, and coefficients
• Reactants


  Substances that are used up to form new substances in a chemical reaction
• Products


  End-results that are formed after a chemical reaction
• State symbols


  (s) - solid, (l) - liquid, (g) - gas, (aq) - aqueous
• Law of Conservation of Mass

  Proposed by French Chemist Antoine Lavoiser, states that mass is conserved in any chemical reaction and atoms are neither created nor destroyed, only rearranged
• Types of Chemical Reactions

  • Combination or Synthesis Reaction
  • Decomposition Reaction
  • Single Displacement Reaction
  • Double Displacement Reaction
  • Combustion Reaction
• Combination or Synthesis Reaction


  A reaction where a new product is synthesized by combination of two or three reactants
• Decomposition Reaction


  A reaction where a compound decomposes or breaks into two or more different products, usually requiring an input of energy in the form of heat, light, and electricity.
• Single Displacement Reaction


  A reaction where a cation (metal) or anion (non-metal) is displaced or exchanged from a compound, usually involving ionic compounds
• Double Displacement Reaction


  A reaction where the cations (metal) and anions (non-metal) of two ionic compounds exchange places to form two new compounds, often involving polyatomic ions
• Combustion Reaction


  A reaction where a substance or compound reacts with oxygen gas (O2), releasing energy in the form of light and heat, producing carbon dioxide (CO2) and water (H2O)
• Balancing Double Displacement Reactions

  1. Find polyatomic ions that don't decompose

  2. Count atoms of each element on both sides
• Polyatomic ion


  A compound in parentheses that is a polyatomic ion
• Balancing chemical equations with polyatomic ions

  1. Adjust first the polyatomic ion, especially if it has an odd subscript

  2. Apply coefficient on the single element on the product side if it is still not balanced with the reactant side
• Single displacement reaction


  A + BC ⟶ AC + B
• Double displacement reactions


  • Usually consist of polyatomic ions
  • Find the polyatomic ion(s) that does not decompose before and after the reaction, and count that as 1
  • Adjust first the polyatomic ion, especially if it has an odd subscript
• Double displacement reactions with no polyatomic ions

  • Find the element/compound with an odd subscript and adjust that first
• Double displacement reactions with an element/compound expressed twice


  • Apply the same tip as for double displacement reactions with polyatomic ions
• Combustion reactions


  • Always have CO2 and H2O as products
  • Use the CHO method: balance first the carbon, then hydrogen, and lastly oxygen
• Balancing combustion reactions with odd oxygen coefficients


  • Multiply all coefficients by 2 to avoid decimals
• Chemical change


  When a substance(s) is transformed into one or more new substances
• Chemical reaction


  The specific process under chemical change where it involves reactants and products
• Chemical equation


  Uses chemical (element) symbols, subscripts, and coefficients to show what happens during a chemical reaction
• Reactants


  The starting materials that are used up to form new substances in a chemical reaction
• Products


  The final, new materials that are formed after a chemical reaction
• The Law of Conservation of Mass states that the mass is conserved in any chemical reaction
• Types of chemical reactions

  • Combination/Synthesis: A + B ⟶ AB
  • Decomposition: AB ⟶ A + B
  • Single displacement: A + BC ⟶ AC + B
  • Double displacement: AB + CD ⟶ AD + BC
  • Combustion: Hydrocarbon + O2 ⟶ CO2 + H2O