6.1 Kinetic Molecular Theory and the Ideal Gas Law

Why are gases “Nature’s Simplest Structures”

• simple models

• calculations are accurate to behaviour

What are the main assumptions of kinetic molecular theory?

1. molecules are small and far apart

2. molecules are in constant, random motion

3. molecules collide w each other + walls of container

4. molecules’ collisions are perfectly elastic

5. molecules only move in straight and only interact thru collisons

6. average translational kinetic energy is directly proportional to temp. in Kelvin

What is the importance of the first assumption of kinetic molecular theory?

since molecules are small and far apart, the majority of the space a gas takes up is empty space

What is the importance of the second assumption of kinetic molecular theory?

there are as many molecules moving in one direction as the other

What is the equation for kinetic energy to kelvin?

KE_avg = (3/2) RT

Why must particles movement be random?`

even if the molecules where moving parallel, the walls of a container are so uneven, that random movement occurs

What is the Ideal Gas Law?

PV = nRT

P = pressure (kPa)

V = volume (L)

n = moles (mol)

R = universal gas constant (mol K kPa⁻¹ K⁻¹)

T = temperature (K)

What is the name for R in the ideal gas law equation?

universal gas constant

Assuming P and n are constant, what is expected if T increases?

volume increases

Assuming T and n are constant, what is expected if V increases?

pressure decreases

Assuming T and V are constant, what is expected if n increases?

pressure increases

When is deviation from ideal behaviour most significant for ideal gases?

1. when P is high

2. when T is very low