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Some Basic Concepts of Chemistry
Mole concept, stoichiometry, concentration and reactions
Key Concepts
- Mole: 6.022 × 10²³ particles (Avogadro's number)
- Molarity (M): moles of solute per litre of solution
- Molality (m): moles of solute per kg of solvent
- Equivalent weight: molar mass divided by n-factor
- Limiting reagent determines maximum product; excess reagent remains
Important Formulae
| Number of moles | n = m/M (mass/molar mass) |
| Molarity | M = n / V(L) |
| Dilution law | M₁V₁ = M₂V₂ |
| Mole fraction | χ_A = n_A / (n_A + n_B) |
| Mass % of solute | (mass of solute / mass of solution) × 100 |
Quick Tips
- 1 mole of any ideal gas occupies 22.4 L at STP (0°C, 1 atm).
- Always balance the chemical equation before stoichiometric calculations.
- n-factor for acid = basicity (H⁺ given); for base = acidity (OH⁻ given); for redox = electrons transferred.
Practice Questions
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