Mole Concept & Molarity Calculator
Moles, Mass, Molarity & Dilution
Convert between mass and moles, calculate molarity, solve dilution problems, and find the number of particles instantly — with full step-by-step working for NEET, JEE, TN Board and CBSE Chemistry.
Choose what you want to calculate
Mole Concept & Molarity Formulas
The mole is the SI unit for the amount of a substance — one mole of anything contains 6.022 × 10²³ particles (Avogadro's Number). The number of moles is found by dividing the given mass by the substance's molar mass.
n = Mass (g) / Molar Mass (g/mol)
Molarity (M) describes the concentration of a solution — the number of moles of solute dissolved per litre of solution.
M = n (mol) / V (Litres)
When you dilute a solution by adding more solvent, the number of moles of solute stays the same — only the volume increases, so the concentration drops. This relationship is captured by the dilution formula:
M₁V₁ = M₂V₂
where M₁, V₁ are the initial molarity and volume (before dilution), and M₂, V₂ are the final molarity and volume (after dilution). Finally, to find the actual number of particles (atoms, molecules, or ions) in a given amount, multiply the number of moles by Avogadro's Number: Particles = n × 6.022 × 10²³.
← Back to Chemistry homework helpMolarity Calculator — Questions Answered
Avogadro's Number (6.022 × 10²³) is defined as the number of particles in exactly one mole of a substance — it was originally derived from the number of atoms in 12 grams of carbon-12. It acts as the bridge between the microscopic world of atoms/molecules and the macroscopic quantities (grams, litres) we can actually measure in a lab.
Add up the atomic masses of every atom in the compound's formula, using the periodic table. For example, water (H₂O) has 2 hydrogen atoms (≈1 g/mol each) and 1 oxygen atom (≈16 g/mol), giving a molar mass of 2(1) + 16 = 18 g/mol.
Diluting means adding more solvent (usually water) without adding any more solute. The total number of solute moles stays exactly the same, but since molarity is moles divided by volume, and the volume has increased, the concentration (molarity) must go down proportionally.
M₁V₁ = M₂V₂ specifically applies to diluting one solution with pure solvent, where moles of solute are conserved. Mixing two different solutions of the same solute uses a related but different approach — adding the total moles from both solutions and dividing by the combined final volume.
Yes — the mole concept and molarity are foundational topics tested directly and indirectly across NEET and JEE Chemistry, since stoichiometry, solutions, electrochemistry and equilibrium calculations all build on these formulas. Check the step-by-step section after calculating to see the exact method expected in exam answers.