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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.
Sample Practice Questions

  1. Atomicity of phosphorus (P₄) is:

    • 1
    • 2
    • 4
    • 8
    Show answer

    Answer: 4

  2. Empirical formula of glucose (C₆H₁₂O₆) is:

    • C₂H₄O₂
    • CH₂O
    • C₃H₆O₃
    • CHO
    Show answer

    Answer: CH₂O

  3. In the reaction 2H₂ + O₂ → 2H₂O, 4g of H₂ reacts with how many grams of O₂?

    • 16 g
    • 32 g
    • 64 g
    • 8 g
    Show answer

    Answer: 32 g

  4. Limiting reagent in a reaction is the one that:

    • Is in excess
    • Gets consumed first and limits product formation
    • Has highest molecular mass
    • Is added last
    Show answer

    Answer: Gets consumed first and limits product formation

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Practice Questions

Practice 20 randomly selected NEET questions on Some Basic Concepts of Chemistry. Answers are revealed after each question.

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