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CHEM 111 Unit 5

Periodic Table Overview

  • Elements are organized by atomic number.

  • Each element has a unique symbol and atomic mass.

  • Common gases, liquids, and solids are distinguished in their placement.

Gaseous Phase Properties

  • Gases consist of molecules/atoms in random motion.

  • Low density and compressible.

  • Homogeneous mixtures; fluids with negligible intermolecular forces.

Pressure in Gases}

  • Defined as the force exerted by gas molecules on surfaces.

  • Pressure formula: p = rac{F}{A}

  • Conversion: 1 atm = 760 mm Hg = 101,325 Pa.

Gas Laws

  • Boyle's Law: P1V1 = P2V2 (volume inversely proportional to pressure at constant T and n).

  • Charles's Law: rac{V1}{T1} = rac{V2}{T2} (volume proportional to absolute temperature at constant n and P).

  • Avogadro's Law: rac{V1}{n1} = rac{V2}{n2} (volume proportional to moles at constant T and P).

  • Ideal Gas Law: PV = nRT (combines all gas laws).

Standard Temperature and Pressure (STP)

  • STP: 0°C (273.15 K) and 1 atm, where 1 mole of gas occupies 22.4 L.

Molar Mass & Density Calculations

  • Molar mass: M_m = rac{m}{n}.

  • Density equations involve molar mass and gas volume: D = rac{m}{V}.

Dalton’s Law of Partial Pressures

  • Total pressure is the sum of partial pressures of individual gases: P{total} = Pa + P_b + ….

Real Gases vs. Ideal Gases

  • Real gases are corrected for interactions and volume (van der Waals equation): rac{P + rac{an^2}{V^2}}{V - nb} = nRT.

Kinetic-Molecular Theory

  • Describes gas behavior based on particle motion; collisions are elastic.

  • Average kinetic energy relates to temperature: KE ext{ (avg)} ext{ is proportional to } T.

Diffusion and Effusion

  • Diffusion: Gas transfer through space; driven by concentration differences.

  • Effusion: Gas transfer through a small opening; rate inversely proportional to molecular mass (Graham's law).