[P Chem] Gaseous State

[PHYSICAL PROPERTIES]

State the SI units of each of the following physical properties:

• Pressure, p

• Volume, V

• Amount of substance, n

• Temperature, T

[PHYSICAL PROPERTIES]

State the SI units of each of the following physical properties:

• Pressure, p

• Volume, V

• Amount of substance, n

• Temperature, T

• Pa

• m³

• mol

• K

[PHYSICAL PROPERTIES]

Convert the following to Pa:

• 1 atm

• 1 bar

• 101325 Pa

• 10^5 Pa

[PHYSICAL PROPERTIES]

Convert the following to m³:

• 1 cm³

• 1 dm³

• 10^-6 m³

• 10³ m³

[IDEAL GAS]

State the ideal gas equation

pV = nRT

[IDEAL GAS]

For a fixed amount of gas, what equation holds true?

p(i)V(i)/T(i) = p(f)V(f)/T(f)

[IDEAL GAS]

Dalton’s Law of Partial Pressures

In a mixture of inert gases at constant volume and temperature, the total pressure of the mixture is the sum of the partial pressures of the constituent gases.

Assuming all gases are ideal,

p(A)/p(T) = n(A)/n(T) → p(A) = (n(A)/n(T))/pT

[IDEAL GAS]

State the four basic assumptions of ideal gas behaviour

1. The volume of gas particles is negligible compared to that of the container

2. There exist no intermolecular forces of attraction between gas particles

3. Collisions between gas particles and with the walls of the container are perfectly elastic

4. Gas particles are in constant random motion

[IDEAL GAS]

State and explain what situations in which the assumptions of ideal gas behaviour do not hold true.

1. At high pressure: since pressure is inversely related to volume, the volume of the gas is relatively small, hence the volume of gas particles becomes significant compared to that of the container.

2. At low temperature: since average kinetic energy of particles is low, particles are unable to overcome intermolecular forces of attraction, making the forces of attraction significant.

[IDEAL GAS]

State and explain the conditions necessary for a gas to approach ideal gas behaviour

1. High temperatures: high average kinetic energy of particles is enough to overcome intermolecular forces of attraction, making them negligible

2. Low pressure: since pressure is inversely proportional to volume, the volume of the gas is relatively large, and volume of particles is negligible compared to that of the container

[IDEAL GAS]

Can an ideal gas be liquefied by cooling and applying pressure? Why or why not?

No, because there are no intermolecular forces of attraction between particles, no matter how you compress/cool it.

[IDEAL GAS]

Explain the relationship between compressibility factor, Z and pressure, p for different gases

1. At very low pressure, Z is approximately 1: all gases exhibit ideal gas behaviour as the volume of gas particles is negligible compared to that of the container

2. At low to intermediate pressure, Z < 1: Gases have a smaller molar volume than ideal gas due to significant intermolecular FoA → more compressible

3. At high pressure, Z > 1: Gases have larger molar volume than ideal gas. Average separation between molecules decreases to the extent where repulsive forces dominate, driving gas particles apart to increase molar volume relative to that of an ideal gas → less compressible

[IDEAL GAS]

Explain the relationship between compressibility factor, Z and pressure, p at different temperatures

As temperature decreases, deviation of real gases from ideality increases.

• Average kinetic energy decreases as temperature decreases → particles get closer together

• Intermolecular forces of attraction become more significant