Chem Unit 8: Gas Laws

Gas General Properties

• particles travel in straight lines

• Collisions create pressure

• fill containers uniformly and completely fast

• Gases expand

• BrINClHOF - diatomics

• Volume -

• Temperature - always in kelvin. When adding 273, its 3 sig figs. (adding sig figs is last decmial place) So when 30 + 273 = 303K. Use 3 sig figs when multiplying.

• n- Moles

• Pressure -

  • measured with a Barometer. Barometer pushes mercury up when pressure pushes down

  • Units: 1 atm = 760 mmhg/torr = 101.3 kPa

• R Constant - 0.0821 (L)(atm)/ (mol)(K)

Gas Formulas

• EVERY CALCULATION IN KELVIN

• UNITS MUST BE THE SAME ON BOTH SIDES

• When we are given STP sig figs don’t count. 0 C, 1 atm

• Boyles Law: P₁⋅V₁ = P₂⋅V₂

  • Inversely Related

  • when all other factors are constant (temp and moles stay the same)

  • If volume of the container increases, the pressure decreases. If the volume increases. If the volume of container decreases, the pressure increases.

  • if double the volume, the pressure 1/2. Opposite is true

  • 

• Gay- Lussac Law: P₁ / T₁ = P₂ / T₂

  • Pressure and Temperature are directly related

  • If the temperature increases, the pressure increases.

  • MUST BE IN KELVIN.

  • if the temperature doubles in kelvin then the pressure doubles. Opposite is true

• Charles Law: V₁ / T₁ = V₁ / T₁

  • Volume and Tempatuer are directly related

  • If the pressure is constant and there is a flexible container, the temperature will increase the collisions, increasing the volume. Example is balloon

  • Must be in Kelvin

• Avagalros Law P/n

  • Adding a gas to a container increases the amount of particles that can collide, increasing pressure. This is a direct relationship. If the pressure exceeds, it will burst the container.

  • When removing

  • This is directly related to so if half of the moles are taken, half the pressure. The opposite is true

• Combined Gas Law (P₁⋅V₁ )/T₁ = (P₂⋅V₂) /T₂

  • Use when Temp Change, Volume Change, Pressure Change. 5 Variables given.

• Ideal Gas Law PV=nRT

  • Constant: R 0.0821 (L⋅ atm)/(Mol⋅K)

• Gas Density

  • At STP 22.4/mol

  • D

• Effusion/ Diffusion and Speed

  • Heaviest is slowest. Pay attention to Diatomic

  • Effusion is going out through a hole

  • Diffusion is high to low

• Daltons Law: P_Total = P_A+P_B

  • Collecting Gas over water. (Total P = water vapor + Gas pressure)

• Grahams Law

Altitude and Volume and Pressure: there is less pressure higher up so volume increases.

• Grahams Law: Rate 1/Rate 2 = (Molar Mass ₂ / Molar Mass ₁)^1/2

  • Rate of effusion is inversely proportional to its molar mass.

  • 

In terms of increasing: low to highest

in terms of decreasing: highest to low

REVIEW THE RATE AND MASS ONE