Chapter 5 - Properties of Gases: The Air We Breathe

(1) Kinetic Molecular Theory (KMT) assumes that gas molecules:

1. Have tiny volumes compared with the collective volume they

   occupy

(2) Kinetic Molecular Theory (KMT) assumes that gas molecules:

2. Move constantly and randomly

(3) Kinetic Molecular Theory (KMT) assumes that gas molecules:

3. All gas molecules in a sample have the same average kinetic

   energy (energy of motion) that is proportional to temperature

(4) Kinetic Molecular Theory (KMT) assumes that gas molecules:

4. Engage in collisions with walls of container and other gas

   molecules

(5) Kinetic Molecular Theory (KMT) assumes that gas molecules:

5. Act independently of other gas molecules

(1) Properties of a Gas

1. No definite shape or definite volume

(2) Properties of a Gas

2. Uniformly fills any container

(3) Properties of a Gas

3. Exerts pressure on surroundings

(4) Properties of a Gas

4. Changes volume with temperature and

pressure

(5) Properties of a Gas

5. Miscible – mixes together in any proportion

(6) Properties of a Gas

6. Much less dense than solids or liquids

(1) Gases can be described by:

1. Volume (V)

(2) Gases can be described by:

2. Temperature (T)

(3) Gases can be described by:

3. Amount (n)

(4) Gases can be described by:

4. Pressure (P)

Pressure (P):

measure of the gas particle collisions with the sides its container; the force (F) exerted by the gas on the surface area (A) of its container

Atmosphere (atm) Unit Equivalent to 1 atm

1 atm (exact)

Millimetres of Hg (mmHg) Unit Equivalent to 1 atm

760 mmHg (exact)

Torr (torr) Unit Equivalent to 1 atm

760 torr (exact)

Pascal (Pa) Unit Equivalent to 1 atm

1.01325 × 10⁵ Pa

Kilopascal (kPa) Unit Equivalent to 1 atm

101.325 kPa

Bar Unit Equivalent to 1 atm

1.01325

Millibar (mbar) Unit Equivalent to 1 atm

1013.25 mbar

Pounds per square inch (psi) Unit Equivalent to 1 atm

14.7 psi

Inches of mercury Unit Equivalent of 1 atm

29.92 inches of Hg

Boyle’s Law states that when T and n are constant, the P of a gas is inversely related to its V

decrease in V = increase in P

increase in V = decrease in P

Inspiration:

air flows into the lungs (aka inhalation)

(1) During inspiration…

1. diaphragm contracts and lungs and ribcage expand

(2) During inspiration…

2. pressure in the lungs decreases

(3) During inspiration…

3. pressure gradient between the lungs and the atmosphere

(4) During inspiration…

4. air flows toward the lower pressure inside the lungs

Expiration:

air leaves the lungs (aka exhalation)

(1) During expiration…

1. diaphragm relaxes, squeezing lungs and lung volume decreases

(2) During expiration…

2. pressure within the lungs increases

(3) During expiration…

3. a pressure gradient between the lungs and the atmosphere

(4) During expiration…

4. air flows from the higher pressure in the lungs to the outside

Boyle’s Law Equation

P₁ x V₁ = P₂ x V₂

P₁ = initial pressure

P₂ = final pressure

V₁ = initial volume

V₂ = final volume

Charles’s Law states that when P and n are constant, the Kelvin T of a gas is directly related to its V

increase in T = increase in V

decrease in T = decrease in V

Charles’s Law Equation

V₁/T₁ = V₂/T₂

Avogadro’s Law states that at constant T and P, the V of a gas is directly related to the number of moles (n) of the gas.

increase in V = increase in n

decrease in V = decrease in n

Avogadro’s Law Equation

V₁/n₁ = V₂/n₂

Admonton’s Law states when V and n are constant, the P exerted by a gas is directly related to its Kelvin T

increase in T = increase in P

decrease in T = decrease in P

Admonton’s Law Equation

P₁/T₁ = P₂/T₂

STP, Standard Temperature and Pressure:

standard temperature (T)

0 °C or 273 K

standard pressure (P)

1 atm (760 mmHg)

At STP:

The volume of 1 mole of gas is 22.4 liters.

This is called its molar volume

22.4 L = 1 mole gas

1 mole gas/22.4 L & 22.4 L/1 mole gas

Ideal Gas Law:

allows the calculation of gas properties when more than one variable is changing

Ideal Gas Law Formula

PV = nRT

R = universal gas constant = 0.08206 L • atm/(K • mol)

P = pressure (in atm)

V = volume (in liters)

n = moles

T = temperature (in Kelvin)

The partial pressure partial pressure of a gas is…

the pressure that each gas in a mixture would exert if it were by itself in the container. Depends on moles (n) of gas, not its identity.

Dalton’s Law of Partial Pressures:

the total pressure exerted by gases in a mixture is the sum of the partial pressures of those gases

P_T = P₁ + P₂ + P₃ +….

Diffusion:

the gradual mixing of gases caused by their motion

Effusion:

the process by which a gas escapes from a container through a tiny hole into a region of lower pressure

both ___ & ___ processes are related to the mass of the particles and how fast the

particles are moving.

diffusion; effusion

Graham’s Law of Effusion: the effusion rate of any gas is inversely proportional to the square root of its MW

lower MW particles = higher effusion rates

higher MW particles = lower effusion rates

effusion rate ∝ 1/√MW