Phase Equilibria Of Pure Substances Flashcards

1
Q

What is relation between entropy of solid,liquid and gas

A

Sm(solid)<Sm(liquid)<Sm(gas)

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2
Q

What is critical temperature Tc

A

Above it liquid and gas are no longer estinguishablr andba single fluid exists called superficial fluid

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3
Q

What is phase boundary line

A

Line at certain pressure where coexist 2 phases

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4
Q

What is relationship between chemical potentials in ohase boundary line

A

μ(α)=μ(β)

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5
Q

Are infinitesimal changes of chemical potential equal?

A

Yes

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6
Q

What formula do we get from equation of equality infinitesimal chemical potential changes

A

ΔSmdT=ΔVmdp

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7
Q

How does Clapeyron equation go

A

dp/dT=ΔSm/ΔVm=(ΔHm/T)/ΔVm

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8
Q

What is formula if there is melting equilibrium

A

p-p0=ΔSm/ΔVm(T-T0)

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9
Q

What is sign of melting slope decided by and what is the most common sign for pure substances,say why and exception

A

By Vm. Its usually + bc Vm(l)>Vm(s); exception is water bc ice is less dense than liquid water and by that molar volume of ice is bigger

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10
Q

What formula do we get from studying evaporation/sublimation boundary line p(α,β)(T)=p*(T)

A

ln(p/p0)=-ΔHm/R(1/T-1/T0)

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11
Q

What are 2 different conditions for evaporation process

A
  1. For the pure substance only(phase coexistance only occurs when p=p*(T)
  2. When also other substances are present in the gas phase
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12
Q

Ahat is nature of many component ideal gas

A

There is no interactions between molecules and each component behaves independently in relation to the others

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13
Q

What is partial pressure of i-th component

A

pi=niRT/V

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14
Q

What is Dalton law

A

Total pressure is sum of partial pressures

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15
Q

What is chemical potential for i-th component

A

μi=μi⊝(T)+RTln(pi/p⊝)

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16
Q

When does equilibrium exist in liquid-vapour relation

A

When chemical potential of 2 phases are equal
μH2O(I)=μH2O(g)=μH2O⊝(T)+RTIn(pH2O*/p⊝)

17
Q

When is there equilibrium between water-acqueous vapour

A

a)if its one component system, when pext=pH2O*
b)pH2O=pH2O* in many component system(partial pressure of acqueous vapour is equal to the vappur pressure pf water in the presence of other gasses)

18
Q

When does water boil

A

When pH2O* arrives to the value of external pressure(with rise of T)

19
Q

What is relative humidity

A

Its equal to pH2O/PH2O*(T)=function of temperature and its often expressed in percentages. If its not 100% we are in “non equilibrium” condition