Chemistry MOLE CONCEPT CHAPTER for NEET & JEE

CHAPTER I-MOLE CONCEPT



Basic Definitions
1. Mole (n): The amount of substance containing as many entities (atoms,

molecules,
ions, electrons, or particles) as there are in 12 g of carbon-12 isotope.
* entities (Avogadro number,

Unit :mol

2. Molar Mass (M):

Mass of 1 mole of a substance.

For element → Atomic mass in grams.

For compound → Molecular mass in grams.

Examples

📌 Example 1
1 mole of H₂O=18g(sincemolarmassofH₂O = 2×1 + 16 = 18).

📌Examples 2
1 mole of O₂ = 32 g, containing molecules of O₂.



Mole Relationships
Relationships to interconvert:

1. Mole ↔ Mass

Ratio of the given mass to the molar mass.

n = (Given mass (g)) / (Molar mass (g/mol))

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, 2. Mole ↔ Number of particles

n = N/NA



3. Mole ↔ Volume (for gases at STP, 1 atm, 273 K)

1 mole gas= 22.4L



📌 Example:
Find number of molecules in 11.2 L of CO₂ at STP.

Ans:

n = 11.2/22.4= 0.5mol




Laws of Chemical Combination
1. Law of Conservation of Mass:

Mass can neither be created nor destroyed.

📌 Example: 2H₂ + O₂ → 2H₂O
Mass before = Mass after reaction.
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