Chapter 10: Gases

Physical properties of gases

Physical properties of gases

All similar characteristics that gases share.

Common gases examples

Oxygen (O₂), Nitrogen (N₂), Carbon Dioxide (CO₂), Methane (CH₄).

Behavior of gases compared to liquids and solids

Gases expand to fill their containers, are highly compressible, and have extremely low densities.

Pressure (P)

The amount of force applied to an area.

Pressure formula

P = F/A

Atmospheric pressure

The weight of air per unit of area.

Units of pressure

Pascals, Bar, mm Hg or torr, Atmosphere.

Standard atmospheric pressure (STP)

1 atm, 760 torr (760 mmHg), 101.325 kPa.

Boyle’s Law

The volume of a fixed quantity of gas at constant pressure is inversely proportional to the pressure.

Charle’s Law

The volume of a fixed amount of gas at constant pressure is directly proportional to its absolute temperature.

Gay-Lussac’s Law

At a given temperature and pressure, the volume of gases that react with each other is in small whole numbers.

Combined Gas Law formula

(P1V1)/T1 = (P2V2)/T2

Avogadro’s Law

The volume of a gas at constant temperature and pressure is directly proportional to the number of moles of gas.

Ideal-Gas Law

PV = nRT, where n is the number of moles of gas and R is the ideal gas constant.

Ideal gas constant (R)

0.08206 L·atm/(mol·K).

Density of gases formula

d = MP / RT.

Dalton’s Law of Partial Pressure

The total pressure of a mixture of gases equals the sum of the pressures each would exert alone.

Mole fraction formula

x1 = n1/nt.

Kinetic-Molecular Theory main tenets

Gases consist of moving molecules, low attractive forces, and energy is transferred in collisions.

Average kinetic energy of molecules

Proportional to the absolute temperature.

Effusion

Escape of gas molecules through a tiny hole.

Diffusion

Spread of one substance throughout space or another substance.

Graham’s Law

Describes the relationship of gas molar mass to diffusion and effusion rates.

Real gases behavior

Conforms to ideal-gas equation only at high temperatures and low pressures.

van der Waals equation

Accounts for deviations from ideal gas behavior: P = [nRT / (V - nb)] - [a(n/V)²].

Corrections for non-ideal behavior

Account for molecular attraction and volume occupied by gas molecules.