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: $P<em>1V</em>1 = P<em>2V</em>2$ (volume inversely proportional to pressure at constant T and n).

• Charles's Law: $rac{V<em>1}{T</em>1} = rac{V<em>2}{T</em>2}$ (volume proportional to absolute temperature at constant n and P).

• Avogadro's Law: $rac{V<em>1}{n</em>1} = rac{V<em>2}{n</em>2}$ (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: $P<em>{total} = P</em>a + P_b + …$.

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).