Chemical Reactions and Types

Chemical Reactions

• Chemical reactions involve the motion of electrons, leading to the formation or breaking of chemical bonds.
• They can be classified as: combination or synthesis reactions, decomposition reactions, single and double displacement reactions, oxidation and reduction.

Combination Reactions

• In combination reactions, two or more substances combine to form a new single substance under suitable conditions.
• They can be classified into three types:
  • Reactions between two or more elements (e.g., hydrogen combining with oxygen to form water).
  • Reactions between two or more compounds (e.g., carbon dioxide dissolving in water to form carbonic acid or soda water).
  • Reactions between an element and a compound (e.g., carbon monoxide reacting with oxygen to form carbon dioxide).

Decomposition Reactions

• In a decomposition reaction, a single compound splits into two or more simple substances under suitable conditions such as heat, light, or electricity.
• Decomposition reactions are classified into three types:
  • Thermal decomposition (e.g., copper (II) carbonate decomposing into copper (II) oxide and carbon dioxide gas when heated).
  • Electrolytic decomposition (e.g., electrolysis of water resulting in the separation of hydrogen and oxygen).
  • Photo decomposition (e.g., silver chloride decomposing into silver and chlorine gas in the presence of sunlight).

Chemical Reactions

• Chemical reactions involve the motion of electrons, leading to the formation or breaking of chemical bonds.
• They can be classified into five types: combination, decomposition, single and double displacement, oxidation, and reduction reactions.

Combination Reactions

• Involve two or more substances combining to form a new single substance under suitable conditions.
• Classified into three types:
  • Reactions between two or more elements (e.g., 2H2 + O2 → 2H2O).
  • Reactions between two or more compounds (e.g., CO2 + H2O → H2CO3).
  • Reactions between an element and a compound (e.g., 2CO + O2 → 2CO2).

Decomposition Reactions

• Involve a single compound splitting into two or more simple substances under suitable conditions (heat, light, or electricity).
• Classified into three types:
  • Thermal decomposition (e.g., CuCO3 → CuO + CO2, when heated).
  • Electrolytic decomposition (e.g., 2H2O → 2H2 + O2, through electrolysis).
  • Photo decomposition (e.g., 2AgCl → 2Ag + Cl2, in sunlight).