๐งช NEB & CEE Chemistry: 50 Most Important MCQs from Physical Chemistry
Mole Concept | Stoichiometry | States of Matter (Gas Laws) | 24 May 2082
๐ Physical Chemistry: Complete Formula Recap for NEB & CEE (24 May)
๐น Mole Concept & Stoichiometry: Mole = mass/Molar mass = Number of particles/Avogadro's number = Volume of gas at STP/22.4 L. Avogadro's number N_A = 6.022 × 10²³. Molarity (M) = moles of solute / Volume of solution (L). Molality (m) = moles of solute / Mass of solvent (kg). Mole fraction = moles of component / total moles.
๐น States of Matter (Gaseous State): Boyle's Law: P ∝ 1/V (at constant T). Charles's Law: V ∝ T (at constant P). Gay-Lussac's Law: P ∝ T (at constant V). Combined Gas Law: P₁V₁/T₁ = P₂V₂/T₂. Ideal Gas Equation: PV = nRT. R = 0.0821 L·atm/mol·K = 8.314 J/mol·K. STP conditions: 0°C (273 K), 1 atm, 22.4 L per mole.
๐น Dalton's Law of Partial Pressure: Total pressure P_total = P₁ + P₂ + P₃ + ... Partial pressure P₁ = (n₁/n_total) × P_total. Graham's Law of Diffusion: Rate₁/Rate₂ = √(M₂/M₁).
๐น Kinetic Theory of Gases: Average KE = (3/2)RT. Root mean square speed u_rms = √(3RT/M). Most probable speed u_mp = √(2RT/M). Average speed u_avg = √(8RT/ฯM).
๐น Real Gases & van der Waals Equation: (P + an²/V²)(V - nb) = nRT. a and b are van der Waals constants (correction for pressure and volume). Compressibility factor Z = PV/nRT. For ideal gas Z = 1.
๐ก Exam Tips: In CEE and NEB, 8-10 questions come from Physical Chemistry. Focus on mole calculations, gas laws, and R constant variations. Memorize STP conditions and conversion between pressure units (1 atm = 760 mm Hg = 101325 Pa). Practice numericals on partial pressure and diffusion.