Mole Concept

Definition of a Mole:

• A mole is the amount of substance that contains 6.022 × 10²³ particles (atoms, molecules, or ions).

• This number is called Avogadro’s number (Nₐ).

Relationship Between Mole, Mass, and Avogadro’s Number

• 1 mole of any substance contains 6.022 × 10²³ particles.

• 1 mole of an element = Atomic mass (in grams).

• 1 mole of a compound = Molecular mass (in grams).

Examples:

• 1 mole of H₂O = 18 g

• 1 mole of CO₂ = 44 g

Numerical Problems Based on Mole Concept

• Example: How many molecules are present in 36g of water (H₂O)?

  • Molecular mass of H₂O = 18 u

  • Number of moles = (36g / 18g) = 2 moles

  • Number of molecules = 2 × (6.022 × 10²³) = 1.204 × 10²⁴ molecules

(Diagram: Step-by-step mole concept calculations for different substances)