Chemical Reactions: Types and Importance

Importance of Chemical Reactions -

• Everyday Examples:

  • Car Fuel: The combustion of gasoline in car engines generates power, contributing to car movement.

  • Photosynthesis: Plants utilize carbon dioxide ($CO2$) and water ($H2O$) in a chemical reaction to produce their own food.

  • Manufacturing: Chemical reactions are essential in the production of medicines, fertilizers, and artificial fibers.

Definitions

• Chemical Reaction: The process of breaking bonds in reactants and forming new bonds in products.

Types of Chemical Reactions

1. Thermal Decomposition Reactions

   • Chemical reactions involve breaking up of compounds by heating into piramry elements or simpler compounds

   • Example: $AB \rightarrow A + B$

   • Types of Thermal Decomposition Reactions:

     • Metal Oxides: Decompose into metal and oxygen.

     • Example: $2 \text{HgO} \rightarrow 2 \text{Hg} + \text{O}_2$

     • Metal Hydroxides: Decompose into metal oxide and water vapor.

     • Example: $\text{Cu(OH)}<em>2 \rightarrow \text{CuO} + \text{H}</em>2O$

     • Metal Carbonates: Decompose into metal oxide and carbon dioxide.

     • Example: $\text{CuCO}<em>3 \rightarrow \text{CuO} + \text{CO}</em>2$

     • Metal Sulphates: Decompose into metal oxide and sulphur trioxide.

     • Example: $\text{CuSO}<em>4 \rightarrow \text{CuO} + \text{SO}</em>3$

     • Metal Nitrates: Decomposes into metal nitrite and oxygen.

     • Example: $\text{NaNO}<em>3 \rightarrow 2 \text{NaNO}</em>2 + \text{O}_2$

2. Substitution Reactions

   • Definition: When an active element replaces a less active element in a compound.

   • Types of Substitution Reactions:

     • Simple Substitution: chemical reaction which an active element replaces (substitute) the less active element in the solution of one of its compounds

     • **!!1) (( An active metal can substitute hydrogen in water )) :

     • Example: 2Na + 2H2O — 2NaOH + H2 ～★☆

     **2) (( Active metal substitute the hydrogen of diluted acid ))

     • Double Substitution: Exchange reaction between ions of two compounds.

     • Example: $\text{NaOH} + \text{HCl} \rightarrow \text{NaCl} + \text{H}_2O$ (neutralization).

Chemical Activity Series (C.A.S.)

• Definition: Arranges metals based on their reactivity.

• Example Order (from most reactive to least):

  • Potassium (K), Sodium (Na), Calcium (Ca), Magnesium (Mg), Aluminum (Al), Zinc (Zn), Iron (Fe), Tin (Sn), Lead (Pb), Hydrogen (H), Copper (Cu), Mercury (Hg), Silver (Ag), Gold (Au).

Oxidation and Reduction Reactions

• Traditional Concept

  • Oxidation: Loss of electrons or the addition of oxygen.

  • Reduction: Gain of electrons or the removal of oxygen.

  • Example Reaction: $\text{CuO} + \text{H}<em>2 \rightarrow \text{Cu} + \text{H}</em>2O$

• Modern Electronic Concept

  • Oxidation: Loss of an electron.

  • Reduction: Gain of an electron.

  • Example Reaction: $2 \text{Na} + \text{Cl}_2 \rightarrow 2 \text{NaCl}$

Summary of