Kinetic Theory

Question 1

Define ‘The mole’, the SI unit for amount of substance

Answer 1

The amount of a substance which contains the same number of particles as there are atoms in 12g of carbon12

Question 2

What is NA

Answer 2

Avogadro’s constant

Question 3

Define avogadro’s constant

Answer 3

The number of molecules per mole

Question 4

What is N

Answer 4

The number of molecules

Question 5

What is n

Answer 5

The number of moles

Question 6

State the equation which links NA, N and n together

Answer 6

n=N/NA

Question 7

What is M

Answer 7

Molar Mass

Question 8

What is Mr

Answer 8

Relative molecular mass

Question 9

What is Mt

Answer 9

Total Mass

Question 10

How would you calculated M using Mr

Answer 10

M=Mr/1000

Question 11

State the equation which links Mt, M and n together

Answer 11

n=Mt/M

Question 12

State Boyle’s law

Answer 12

For a fixed mass of gas at constant temperature, pressure is inversly proportional to the volume it occupies.
P∝1/v

Question 13

Pressure ∝ Temperature when ____ is constant

Answer 13

Volume

Question 14

Volume ∝ Temperature when ____ is constant

Answer 14

Pressure

Question 15

State the ideal gas equation

Answer 15

pV=nRT
R=molar gas constant

Question 16

State the alternative ideal gas equation using ‘N’ rather than ‘n’

Answer 16

n=N/NA pV=N/NA RT
k=R/NA pv=NkT

Question 17

Kinetic theory assumptions of an ideal gas

Answer 17

1. Intermolecular collisions between molecules are elastic
2. The molecules themselves occupy a negligible fraction of the container volume
3. Repulsive forces only exist when the particles are close enough to one another
4. There is a large number of molecules even in a small volume, with a large number of collisions in a small amount of time
5. The motion of molecules is evenly distributed over all directions
6. There is a random distribution of energy amongst the particles.

Question 18

Kinetic theory of gas pressure equation

Answer 18

Pressure=Mean force/ Area

Question 19

State an equation that combines newton’s laws of motion and the kinetic theory assumptions

Answer 19

p=1/3 ρc² or p=1/3 Nmc²
But C is mean square speed
m=individual mass

Question 20

Combine the ideal gas equation and the gas pressure equation

Answer 20

p=Mt/V = Nm/V
p=1/3 ρc² =1/3 Nmc²/V
pV=1/3 Nmc²
pV=nRT
1/3 Nmc²=nRT
x 3/2
1/2 Nmc²=3/2 nRT

N=Number of particles
1/2 mc²= mean Ek of each particle
1/2 mc²= total Ek of all particles

Question 21

For a Monatomic gas, give the equation for translational Ek of a gas molecule if the total translational Ek is given by Ek=3/2 nRT

Answer 21

3/2 nRT= N 1/2 mc²
Divide each side with N
3/2 x n/N x RT=1/2 mc²
n/N=NA
3/2 x RT/NA =1/2 mc²
R/NA= K
3/2 kT=1/2 mc²