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Physical Chemistry

Mole concept, stoichiometry, thermodynamics, chemical equilibrium, and solutions

Key Concepts
  • Mole concept and stoichiometry underpin all quantitative chemistry
  • Thermodynamics: spontaneity is decided by Gibbs free energy
  • Chemical equilibrium: Le Chatelier's principle predicts the shift
  • Electrochemistry: the Nernst equation relates EMF to concentration
  • Chemical kinetics: rate laws are determined experimentally
Important Formulae
Number of moles n = m/M
Ideal gas law PV = nRT
Gibbs free energy ΔG = ΔH − TΔS
Kp from Kc Kp = Kc(RT)^Δn
Nernst equation E = E° − (RT/nF) ln Q
First-order half-life t₁/₂ = 0.693/k
Quick Tips
  • Always balance the equation before any stoichiometric calculation.
  • ΔG < 0 means spontaneous; ΔG = 0 means equilibrium.
  • For gases, 1 mole occupies 22.4 L at STP.
Sample Practice Questions

  1. The number of moles in 36 g of water (molar mass 18 g/mol) is:

    • 1
    • 2
    • 0.5
    • 18
    Show answer

    Answer: 2

  2. Avogadro's number is approximately:

    • 6.022×10²³
    • 3.0×10⁸
    • 1.6×10⁻¹⁹
    • 9.1×10⁻³¹
    Show answer

    Answer: 6.022×10²³

  3. The molar volume of an ideal gas at STP is:

    • 1 L
    • 22.4 L
    • 24.8 L
    • 18 L
    Show answer

    Answer: 22.4 L

  4. For a spontaneous reaction, the Gibbs free energy change ΔG is:

    • Positive
    • Negative
    • Zero
    • Infinite
    Show answer

    Answer: Negative

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Practice Questions

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