Chemistry - Gas Laws - Unit 9 ✅

U9: Ideal Gas Postulates

1) the volume of gas particles is so small compared to the distance between them that the volume is assumed to be negligible

2) gas particles exhibit NO INTERMOLECULAR INTERACTION with their surrouding or other gas molecules/particles

3) gas particles are in constant, random, rapid straight lines of motion, colliding with eachother and the sides of the container

4) gas particles have elastic collisions with eachother and the walls of the container (conservation of energy)

U9: What does each ideal gas postulate contradict

Negligible volume = matter has mass, its small but there

No IMFS = All molecules are some type of weak London dispersion

Constant, random, straight line movement = gravity and magnetism can cause predicted and bent movement

Total elastic collisions = a small amount of energy is lost with collision

U9: Ideal Gases

Real gases behave most like ideal gases under high temperatures and low pressure

U9: Pressure of gas

Measuring the collisions of gas particles within a container

U9: What is the relationship between temperature and volume

Linear

As temperature decreases, volume decreases

As volume increases, temperature increases

V1/T1=V2/T2 (both go up or both go down)

Always use KELVIN!

U9: What is the relationship between temperature and pressure?

Gay-Lussacs Law (constant volume)

Direct, linear relationship

Temp increase, pressure increase and temp decrease, pressure decrease

Why? Temp increase = more kinetic energy = more collisions = higher pressure

U9: Before doing any equations you must..

Convert to kelvin and make sure the units are the same (both atp or both kPa)

U9: What gases are most likely to act like ideal gases?

Hydrogen and Helium

U9: Can volume be negative (absolute zero)

NO NEVER! This is because we never know the particles exact location and/or movement

Thus, we MUST use kelvin because Celsius will give us 0

U9: Pressure

Force applied to an object by another object

Pressure = force/area

Units= atmospheres (kPa) or kilopascals (kPa)

1 atm=101.3kPa

What's the relationship between pressure and volume?

BOYLES LAW

—> INVERSE

As pressure decreases, volume increases. Constant temp.

This is because: air inside can expand with less pressure and take up more volume ex: balloon

Note: THIS IS AN EXPONENTIAL RELATIONSHIP meaning it's a more sloped relationship if graphed and not a straight line

VOLUME AND PRESSURE NEVER REACH ZERO

P1xV1 = P2xV2

Avogadros Law ⭐️

At constant temperature

V1/n1 = V2/n2

At standard STP (temp and pressure) the volume of a gas is directly related to the number of particles in the container

The volume the moles occupies does not differ between substances.

1mole = 22.4L (IDEAL gas)

How much volume does one mole take up ⭐️

22.4L

When does the number of gas molecules/particles change?

ONLY if gas is added or removed

Kinetic Molecular Theory

Constant random motion:

Gas particles are in constant, random motion, moving in straight lines until they collide with other particles or the container walls.

Negligible particle volume:

The combined volume of the gas particles is negligible compared to the volume of the container they occupy.

No intermolecular forces:

Gas particles exert no attractive or repulsive forces on one another except during collisions.

Elastic collisions:

Collisions between gas particles and the container walls are perfectly elastic, meaning no kinetic energy is lost during collisions.

Average kinetic energy proportional to temperature:

The average kinetic energy of the gas particles is directly proportional to the absolute temperature of the gas.

What conditions are needed for the same number of particles?

Same volume, pressure, temp (Avogadro)

Under which conditions of pressure and temp is a real gas like an ideal gas ⭐️

Low pressure and high temp

Or small particles/radius