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IMG_0001_NEW_0019 - Direction of heat flow AS Example...

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h4 . TODAY'S LECTURE: "Spontaneity, Entropy and Free Energy" . Absolute Entropies . Third Law of Thermodynamics AS and spontaneity Free energy (G) AS and Spontaneity Second Law of Thermodynamics: In any spontaneous process, there is always in increase in the entropy of the universe N.rir."r.: ASsystern * ASr,r.,ooodings > 0 . Foraparticularprocess: A*B t C = Nr-r*oaioo is positive! Spontaneous in the A+B*>e written direction - tfrn+' Spontaneous in the C-2 A+8 opposite direction '>- sWL. . AS-i"o*. : 0 + System at€ggl|llg Ff4: no change rn erther drectton . Example: Water freezing H'O(D + HrQ(s) : AS,,*- is negative (vtua "tet ) -' eltua(j! But Exothermic! + heat flows into surroundings AS"urroundinss and Heat FIow Heat flor,r' l#*.d;FF \*W.=;rffi Sign of AS"urroundings depends on direction of heat flow . Heat: Energy
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Unformatted text preview: + Direction of heat flow + AS . Example: Exothermic reaction Flow of heat: system -) surroundings + random motion of surroundings increases + A,Sru,r> 0 . Endothermic reaction: ASruo< 0 . Heat flow: AH (at constant P) Absolute Entropies Third Law of Thermodynamics: The entropy of a perfect crystal at 0 K is zero T>OK 'o(Do s €r f O Cldo O dGD S,O q Gs4*@ Lattice vibrations-+ Many arrangements =S>0 T:0 K 't{D {t.€to €t€locl€D C€D{*OO OED€D.€DO <tOO{tDCD Only I arrangement =+ S:0 Standard Entropy (S') SF : 5(298 K, I atm) - ^S(0 K, I arn) (tabulated) For a chemical reaction: Nl*",,on = | sf,,"a,* -Z s\*o*,,, S = State function @athway independent) S: Extensive property (depends on amounts z of substances present)...
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