george notes

Question 1

Ideal gas equation

Answer 1

PV=1/3NM =2/3 N(1/2m

Question 2

ideal gas heat capacity relation

Answer 2

Cp=Cv+R

gamme = Cp/Cv

Question 3

ideal gas relation to U

Answer 3

PV=2/3 U

PV = U(gamma-1)

Question 4

monotomic ideal gas heat capacity

Answer 4

C_v = 3/2 R Cp+5/2 R
hence
gamm = 5/3

Question 5

diatomic ideal gas heat capacity

Answer 5

Cv=7/2R Cp=9/2 R

gamma =9/7

Question 6

four steps to the Carnot cycle

Answer 6

isothermal expansion
adiabatic expansion
isothermal compression
adiabatic compression

Question 7

engine efficiency equation

Answer 7

e=WQ=Q1-Q2/Q1 = 1-Q2/Q1

Question 8

alternative form of the engine efficiency equation for the carnot engine

Answer 8

e=1-T2/T1

Question 9

entropy equation

Answer 9

S=Q/T

Question 10

entropy of adiabatic expansion

Answer 10

entropy of adiabatic expansion is constant

S(V,T) = NKb[lnV+1/(gamma-1) lnT] +a

Question 11

first and second law of thermodynamics written together

Answer 11

du=dq+dw

du = Tds+ (-)PdV

Question 12

how many thermodynamic processes does a system with 2 degrees of freedom have and what are they

Answer 12

4 thermodynamic processes

du = Tds - PdV
dH =TdS + VdP Enthalpy
dF = -SdT - PdV Helmholtz free energy
dG = -SdT + VdP gibbs

Question 13

what does enthalpy represent

Answer 13

the heat transfer at constant temperature

H=H(P,V) = U + PV

Question 14

what does Helmholtz and Gibbs free energy describe

Answer 14

they describe processes at constant temperature

F=F(T,V) =U -TS

Question 15

what is the decrease in the Helmholtz energy

Answer 15

It is the maximum amount of work that may be extracted from a system during an isothermal change

Delta F = Delat U - T(Delta) S

Question 16

reactions go in which way to favour the Gibbs?

Answer 16

Reactions go to minimise the Gibbs, it is constant for a reversible process at constant Temperature and pressure

Question 17

what is the gibbs used to determine

Answer 17

the equilibrium states for a system with several phases

Question 18

coefficient of performance for a backwards engine

Answer 18

Tc/Th-Tc = heat out / workdone

approx. 10 for a backwards carnot engine e.g. fridge

Question 19

coefficient of performance of a heat pump

Answer 19

COP = |Qc|/W = Qc/Qh-Qc

Question 20

coefficient of performance for a carnot heat pump

Answer 20

COP = Tc/Th-Tc

Question 21

Boyles law curve at different temperatures

Answer 21

at high temperatures isotherms approx. to boyles law curve. at lower temperatues the boyles law curve becomes distoreted.

Question 22

liquids compressible?

Answer 22

liquids are pretty incompressible

Question 23

what equation is a good approximation for O2 and N2

Answer 23

the ideal gas equation is good approximations for O2 and N2 because roomt T»Tc for these solutions

Question 24

The Clausius -clapyron equation

Answer 24

dp/dT=1Delta(S)/Delta(V) = L/T(Delta)V
where L is latent heat (absorbed)
Delta S is the change in entropy from phase 1 to phase 2

Question 25

equation for three phases to co exist

Answer 25

g1=g2=g3

Question 26

liquid to vapour transient equation

Answer 26

dp/dT = L/ Tb(Vg-Vl) where Tb is boiling temp Vg is gas volume Vl is liquid volume

Question 27

how many constraints does the triple point have

Answer 27

it has three constraints often the entropy increases when changing phase with increasing T

Question 28

why do liquids cool as they evaporate

Answer 28

they lose the more enegetic molecules

Question 29

what is intermolecular potential energy characterised by

Answer 29

the equilibrium separation ro and depth of the well e

Question 30

Van der Waals forces equation

Answer 30

(P+a/Vm^2)(Vm-b)=RT

Question 31

what do a stand for in the van de waals equation

Answer 31

The parameter a allows for the long-range intermolecular attraction which serves to lower the observed pressure

Question 32

what does b stand for in the van der waals equation

Answer 32

the parameter b can be viewed as an excluded volume in a gas due to the present of the molecules (i.e. due to hard core repulsion)

Question 33

what are intermolecular forces proportional too

Answer 33

the number of neighbours and collision frequency so f^2

Question 34

when does the van der waals equation break down

Answer 34

for temperatures below the critical temperature. it is only good for small constraints

Question 35

the entropy change during melting

Answer 35

Delta S f= mLf/Tf

Question 36

Nernest-simon formulation of the third law

Answer 36

if Delta S is the entropy change during any reversible isothermal process ina condensed system then Delta S tends to zero as the temperature goes to absolute zero

Question 37

what is the order of phase transition

Answer 37

the order of phase transition is defined as the order of the lwest differential of the Gibbs function which shows a discontinuity at the transion