Comprehensive notes on Gases, Gas Laws (Boyle's, Charles's, Avogadro's), Ideal Gas Equation, Dalton's Law, Graham's Law, KMT, and Real Gases vs Ideal Gases.
Boyle's Law: Volume is inversely proportional to Pressure at constant Temperature (V ∝ 1/P). PV = k. P1V1 = P2V2.
Charles's Law: Volume is directly proportional to Absolute Temperature at constant Pressure (V ∝ T). V/T = k. V1/T1 = V2/T2.
Avogadro's Law: Volume is directly proportional to number of moles at constant P and T (V ∝ n). 1 mole of any ideal gas at STP occupies 22.414 dm3.
Combine gas laws: PV = nRT. R (Ideal Gas Constant): 0.0821 dm3 atm K-1 mol-1 or 8.314 J K-1 mol-1 (SI unit).
Density of Gas: d = PM / RT. (M = Molar Mass).
Total pressure of a mixture of non-reacting gases is equal to the sum of their individual partial pressures. Ptotal = P1 + P2 + P3 ...
Partial Pressure: Pgas = Xgas × Ptotal (where Xgas is mole fraction). Application: Collecting gas over water (Pdry_gas = Ptotal - Pwater_vapour).
Rate of diffusion/effusion is inversely proportional to the square root of density (or molar mass) at constant P and T.
Rate ∝ 1/√d. r1/r2 = √(d2/d1) = √(M2/M1).
Postulates: 1. Molecules are in constant random motion. 2. Collisions are perfectly elastic. 3. No attractive/repulsive forces. 4. Actual volume of molecules is negligible compared to total volume.
Kinetic Equation: PV = 1/3 mNc2 (where c2 is mean square velocity).
Real gases deviate from ideal behavior at Low Temperature and High Pressure due to intermolecular forces and finite volume of molecules.
Van der Waals Equation: (P + an2/V2) (V - nb) = nRT. 'a' corrects pressure (forces), 'b' corrects volume (excluded volume).