Burdge/Overby, Chemistry: Atoms First, 2e Ch14 | Page 24
SEC TION 14.5 ? Predicting Spontaneity
593
molecules from solid to liquid. Conversely, for the water-to-ice transition, the decrease in entropy
is given by
–6010 J/mol
?Swater ice =? ___________?
??
??? –22.0 J/K ? mol
=
273 K
The same approach can be applied to the water-to-steam transition. In this case, ?H is the heat of
vaporization and T is the boiling point of water.
Worked Example 14.7 examines the phase transitions in benzene.
Worked Example 14.7
The molar heats of fusion and vaporization of benzene are 10.9 and 31.0 kJ/mol, respectively.
Calculate the entropy changes for the solid-to-liquid and liquid-to-vapor transitions for benzene.
At 1?atm pressure, benzene melts at 5.5°C and boils at 80.1°C.
Strategy The solid-liquid transition at the melting point and the liquid-va ? ?[??][?] H??[[???[?\?H\]Z[X??][H ???\??\?\?Y??K?X?]\?H8?!??\? ?\??]\]Z[X??][K[?XX??\?H ?B??[? \?H\]X][? M ?L ?X??] ][?? ??8?!??[? ?? ?[????8?!?? ?]\?Z[?H H[? ?? H?[??B?\????X]Y ?] H ???\????] \HY[ [?? ?[???[??[?H\?
K?H
? ???MHH ?? ???[? H??[[?? ?[?\? ?H
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?????8?&H[?8? ?? ??? ?? ?
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p???RL? ?B??L??Bx?!? ?X?H
?????[???M ?K??H] ?] [\\?] \?H
[?0??H?\?H ?XX?[??????H?Z[??????[?[?\? ???[?[?\?Y?]\?8?!?H M?x?+???[?[?8?!??H M?H???8?&H[????\?LLN
?? M?M? M? ?[?
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