Second Principle Of Thermodynamics

Question 1

What is additional constraint for irreversible transformations

Answer 1

Spontaneity. Heat is tranferred from warmer to cooler object

Question 2

What is entropy

Answer 2

Measure of disorder at the microscopic pevel

Question 3

What is enunciation of the 2nd principle

Answer 3

1. For any closed system there is state finction entropy S whose variations can be calculated by integration along reversible tranformations
   •dS=(dq/T)rev
2. Each adiabatic process fulfills the constraint: ΔSad≥0(it can be =0 for reversible transformations but for spontaneous(irreversible) its strictly >0)

Question 4

Formula for ΔS regarding S(final) and S(initial)

Answer 4

ΔS=S(final)-S(initial)

Question 5

What kind of state function is entropy

Answer 5

Extensive. S=S(T,p,n)

Question 6

Is ΔSad<0 possible?

Answer 6

No

Question 7

What is 3rd principle of thermodynamics

Answer 7

The entropy of perfect crystalls(without defects) of pure substances is equal to 0 at T=0K

Question 8

Using third principle what is formula for ΔS

Answer 8

ΔS=S(final)-S(0K)=S(final)

Question 9

Formula for dSm

Answer 9

dSm=(dq/T)=dHm/T=c(p)dT/T

Question 10

What is formula for ΔSm

Answer 10

•ΔSm=(Up=T2; Down=T1)∫dTcp(T,p)/T
•If cp=almost constant and ΔT=T2-T1 is small
ΔSm=cp∫dT/T=cpln(T2/T1)

Question 11

What is fusion entropy

Answer 11

•ΔfusS=molar entropic variation of pure substance X at p=const

Question 12

What is formula for ΔfusS

Answer 12

If the transformation goes through reversible process(p=const,Wvol),entropy for 1mol of substance is:
•ΔfusS=ΔfusH/T(fus)

Question 13

What is ΔSad for adiabatic system of thermostat and another system

Answer 13

q(sys)=ΔfusH
q(term)=-ΔfusH
•ΔSad=S(sys)+S(term)=ΔfusH/T(fus)+(-ΔfusH)/T(term)=ΔfusH((T(term)-T(fus))/T(term)*T(fus))

Question 14

What are characteristics of ΔSad when
a)Tterm>Tfus
b)Tterm=Tfus
c)Tterm<T fus

Answer 14

a)ΔSad>0=>irreversible/spontaneous process
b)ΔSad=0=>reversible melting process
c)ΔSad<0=>impossible

Question 15

What is Gibbs free energy

Answer 15

Its extensive quantity whose absolute value us unknown. Its used to describe equilibrium at given T and p

Question 16

What is formula for Gibbs free energy

Answer 16

G=H-TS=U+pV-TS

Question 17

What is fundamental property of G

Answer 17

G≤0
Where it can be G=0 for reversible processes. For irreversible its strongly <0

Question 18

What is G a function of and what kind of property is it

Answer 18

T,p,n. Extensive

Question 19

What is molar Gibbs free energy

Answer 19

G for 1 mol of substance
Gm(T,p)=G(T,p,n)/n
Its also called chemical potential, with a sign μ
G(T,p,n)=n*μ(T,p)