A mole is a counting unit used in chemistry. 1 mole = 6.022 × 10²³ particles (atoms, molecules, ions, electrons, etc.). It's similar to a dozen (12 items) or a gross (144 items), but for subatomic scales where we deal with enormous numbers.
A mole is simply a counting unit — like a dozen (12) or a gross (144). One mole = 6.022 × 10²³ particles (atoms, molecules, ions). This huge number (Avogadro's number) lets chemists scale up from individual atoms to measurable amounts of stuff in the lab. If you know molar mass, you can convert grams to moles and then to the number of particles. This concept shows up in every NEET chemistry calculation.
NEET Frequency: 3-4 questions per year
Avogadro's number (6.022 × 10²³) is defined so that the mass of 1 mole of an element in grams equals its atomic mass number. For example: ¹²C has atomic mass 12 amu, and 1 mole of ¹²C weighs exactly 12 grams. This link between atomic mass (tiny) and molar mass (measurable) is the whole point.
First, find molar mass (M) from the periodic table. Then: moles = mass (g) ÷ M (g/mol). Then: particles = moles × 6.022 × 10²³. Example: 18 g of H₂O = 18 g ÷ 18 g/mol = 1 mol = 1 × 6.022 × 10²³ = 6.022 × 10²³ molecules.
Molarity (M) = moles of solute ÷ liters of solution. It depends on volume at a specific temperature (volume expands when warm). Molality (m) = moles of solute ÷ kilograms of solvent. Molality doesn't change with temperature. NEET usually asks about molarity.
At STP (0°C, 1 atm), ideal gas molecules have a specific average kinetic energy. Using PV = nRT (ideal gas law), 1 mole of gas at these conditions occupies 22.4 L. At room temperature (25°C), it's about 24 L. Always check which temperature is given in the problem.
Visualize mole concept & avogadro's number — neet explained with an interactive 3D simulation.
Explore 1 Particle vs 1 Mole Lab→