Gas laws and Kinetic theory (CH20)

Includes the three gas laws and the equation of state.

What is Boyle’s law?

• Iso-thermal, the temperature is kept constant

• Pressure and volume are indirectly proportional

• p1V1 = p2V2 = p3V3

What is Charle’s Law?

• Iso-baric, pressure is kept constant

• Temperature and volume are directly proportional

• V1/T1 = V2/T2 = V3/T3

Graph must be in Kelvin to go through the origin.

What is Gay-Lussac’s law?

• Constant volume

• Temperature and pressure are directly proportional

• P1/T1 = P2/T2

Graph must be in Kelvin to go through the origin.

What is Brownian motion?

the term to describe the random motion of particles in a gas or liquid

What is avogadro’s number?

The number of particles in 1 mole

(on equation sheet)

What is molarity?

The number of moles, n

What is molar mass?

The mass of one mole, M or Mr

How does pressure occur/what makes it happen?

Pressure is the average force of gas particles on the walls of the container. p = F/A in pascals or N/m².

• Particles in a container collide with the walls of the container

• When colliding with the walls, they exert a force on the wall, and the wall exerts a force on the particles (according to Netwton’s 3rd)

Give an example of Brownian motion

• pollen grains in water

• dust motes in air

How does Brownian motion occur?

For pollen grains in water:

• particles in the water are moving around each other

• The particles collide with the pollen grains

• This results in pollen grains appearing to move around randomly

What is the equation of state? When is it used?

• It describes the state of a gas

• Used when only the molarity is kept constant.

Write an equation (not of state) for a constant n.

(p1V1)/T1 = (p2V2)/T2

What is n equal to in the equation of state?

The molarity.

What is R equal to in the equation of state?

The gas constant.

What units must temperature be in for the equation of state?

Kelvin

Use pV = nRT to explain the three gas laws.

• Isothermal, rearrange for T to get pV

• Isobaric, rearrange for p get V/T

• Constant volume, rearrange for V to get P/T

What two units can R be measured in?

• J/(Kmol) - on the equation sheet

• atmL/Kmol - not on equation sheet but might be given

atm = atmospheres L = litres K = Kelvin mol = moles J = joules

What is the conversion for atmospheres to Pascals?

x10^5

What is the conversion for Litres to m³?

x10^-3

How can density be used in the equation of state?

p = ρ/M x RT

When would pV = NkT be used?

When using the number of particles in a substance instead of moles.

What is k?

The Boltzmann constant.

What is m?

The mass of a substance

Derive the equation for the kinetic theory of gas molecules

See sheet.

How is the absolute zero of temperature interpreted in terms of ideal gas laws?

(Charles/Gay-Lussac)

Pressure or volume is plotted against temperature. The data is extrapolated, and where the line crosses the temperature axis, it is absolute zero. (Or when pxV = 0 or p = 0)