Chemistry 116 - Exam 1 Concepts

What is the defining property of gases?

Gases assume the volume of their container (expand to fill space).

Why are gases compressible?

Gas particles are far apart with lots of empty space.

Are gases homogeneous or heterogeneous mixtures?

Always homogeneous.

Do gases mix easily?

Yes — they mix uniformly due to constant motion.

Boyle’s Law?

Pressure ↑ → Volume ↓ (T constant)

• Formula: PV = k

Charles’ Law?

Temperature ↑ → Volume ↑ (P constant)

• Formula: V/T = k

Avogadro’s Law?

Moles ↑ → Volume ↑ (T, P constant)

• V/n = k

Combined Gas Law?

All three variables change (P, V, T)

• Formula: P₁V₁/T₁ = P₂V₂/T₂

  • When temp is constant in a given problem, temp can be ignored

Ideal Gas Law

PV = nRT

• R = 0.08206 Latm/molK or 8.314 Jmol/K

• T is alway in kelvin

Gas density formula?

d = PM/RT

• M = molar mass (g/mol)

Ideal gases have no….

intermolecular forces

Ideal gases have….

negligible volume & no chemical attraction

Ideal gases behave ideally at….

high T, low P

Real gases deviate at….

low T, high P

Higher molar mass →

higher density

Higher pressure →

higher density

Higher temperature →

lower density

Lighter gases effuse….

faster

• Fast RMS speed

• RMS number is larger

Heavier gases effuse….

slower

• Slow RMS speed

• RMS number is smaller

Effusion Formula for TIME

t₁/t₂ = square root of (M₁/M₂)

Monometer concept: Gas side lower →

gas pressure higher

• Formula: Pressure given + pressure height difference

Monometer concept: Gas side higher →

gas pressure lower

• Formula: Pressure given - pressure height difference

Monometer concept: Height difference = ….

pressure difference

Partial pressure = ….

mole fraction × total pressure

• Mole fraction: moles of A / moles totoal

Sum of mole fractions =….

1

0 K = how much in celcius?

–273 °C

Volume extrapolates to zero at….

absolute zero

Lighter gases move….

faster

• High RMS speed

RMS speed depends on….

temperature and molar mass

Gay-Lussac’s Law

Pressure is directly proportional to temeperature

• Formula: P/T = k

Root-mean square speed

V_rms = square root of 3RT / M_m

• M_m = kg/mol