Ideal gases

Question 1

Mole def

Answer 1

One mole is the amount of substance that has the same number of particles as there are atoms in 0.012kg of carbon 12

Question 2

Mass of molecule formula

in terms of RAM, Av

Answer 2

Mass of molecule= RAM/ Avagadro

Question 3

Number of moles formula

Answer 3

Mass/ RAM

Question 4

Number of particles formula

Answer 4

Number of moles * Avagadro

Question 5

Ideal gas definiton

Answer 5

An ideal gas is one that obeys PV∝T at all pressures volumes and temperatures

Question 6

Boyles law

Answer 6

V∝1/P

Question 7

Charle’s law

Answer 7

V∝T

Question 8

Pressure law

Answer 8

P∝T

Question 9

Ideal gas equation

Answer 9

PV= nRT
PV= NKT

n is number of moles
N is number of molecules

Question 10

K is?

Answer 10

Boltzmann’s constant
K=R/ Avagadro

Question 11

Ideal gas equation is only used for?

Answer 11

real gases well above liquefaction temp with not high pressure

Question 12

4 Basic assumptions of kinetic theory of gases

Answer 12

1. Gases contain large molecules moving randomly with negligible attraction between molecules
2. Forces between particles are negligible, except during collisions- which are perfectly elastic
3. Volumes of the particles is negligible compared to the volume occupied by the gas
4. The time of collision by a particle with the container walls is negligible compared with time between collisions

Question 13

What are the 4 assumptions about

Answer 13

Attraction between molectules
Forces between particles
Volume of particle
Time of collision of particle

Question 14

Derivation of PV= 1/3Nm<c²>

6 points

Answer 14

1. ΔP after hitting a wall at 90°. ΔP= -2mc
2. Time between collisions. t= 2l/ c
3. Combine to find ΔP/t= F. F= 2mc/ (2l/c) = mc²/l
4. Pressure P= F/A. = mc²/l ÷ l² = mc²/ l cubed
5. Different speeds of dif molecules, use <c²> and NM
   P= Nm<c²>/ l cubed
6. Three different directions of molecules
   P= 1/3 Nm<c²>/ l cubed

Question 15

Pressure exerted by gas formula

Answer 15

P= 1/3Nm<c²>/ V

Question 16

Mean speed?

Answer 16

<c>= all speeds/ no. of speeds
</c>

Question 17

Mean square speed

Answer 17

<c²>= all speeds squared/ number of speeds

Question 18

R.m.s

Answer 18

√<c²>= root of <c²>

Question 19

Derive kinetic energy= 3/2kt

3 points

Answer 19

1. state two formulas: PV= 1/3Nm<c²> and PV= NkT
2. Equate
3. Simplify to get kinetic energy

Question 20

Why is the value of Boltzmann’s constant so small

Answer 20

Because the increase in kinetic energy of a molecule is very small for every incremental increase in temperature

Question 21

What is Boltzmann’s constant

Answer 21

Relates the properties of microscopic particles (ke of gas molecules) to their macroscopic properties (temperature)