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# Clausius Clapeyron Equation - Thermochemistry Chemistry Notes | EduRev

## Physical Chemistry

Created by: Asf Institute

## Chemistry : Clausius Clapeyron Equation - Thermochemistry Chemistry Notes | EduRev

The document Clausius Clapeyron Equation - Thermochemistry Chemistry Notes | EduRev is a part of the Chemistry Course Physical Chemistry.
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Clausirs Clapeyron Equation: The two phases in equilibrium may be any of the following types:

(i)  Solid and Liquid, S L, at the melt ing point of the solid.

(ii)  Liquid and vapour, L V, at the boiling point of the liquid.

(iii)  Solid and vapour, S V; at the sublimat ion temperature of the solid. “The equal amounts of a given substance must have exactly the same free energy in the two phases at equilibrium with each other.”

Consider t ype equation A B at the given temperature and pressure. If G& GB be the free energy per mole of the substance A & B in initial.
Then, G= GB
Hence ΔG = GB - GA = 0 ΔG = GB - GA = 0
If temperature of the system raise from T to T + dT then pressure raise from P to P + dt, in order to maintain the equilibrium. The free energy of substance raise from GA to GA + dGand GB + dGB. Since the two phase are still in equilibrium hence,
CA = dGA = GB + dG                                            [∵ GA = GB]
then dGA = dGB                                          …(a)

According to thermodynamics, dG = VdP – SdT

dGB = VBdP – SBdT

Using equation (a) and (b)

we get

dGA = dGB  V& VB be the volume of A and B.

If q heat exchanged reversibly per mo le of substance during the phase transformat ion at temperature t, then change in entropy. Δ Hence, Thus, This is Clapeyron equation.
Claypeyron equation for liquid vapour equilibrium where

ΔH= heat of vapourisation
Vg = volume of gas
Vl = volume of liquid
⇒ [∵ Vg >> Vl]
& PV = RT (per mole) ⇒ ⇒ ⇒ ⇒ ⇒ This is Clasusius-Clapeyron equation.
Claypeyron equation for solid vapour equilibria
Solid Vapour

ΔHS = heat of sublimation Vg >> V& Similarly the above equation, we get  Claypeyron equation for solid liquid equilibria

Solid Liquid

ΔH= heat of fusion   Offer running on EduRev: Apply code STAYHOME200 to get INR 200 off on our premium plan EduRev Infinity!

## Physical Chemistry

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