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Thermodynamics and Thermochemistry
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Entropy and second law, entropy changes in processes
NEET level
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td121
According to the third law of thermodynamics, the entropy of a perfectly crystalline pure substance at absolute zero is
A
equal to
R
B
infinite
C
zero
D
equal to its enthalpy of fusion
Answer: C
At
0
K
a perfect crystal has only one microstate, so
S
=
k
ln
1
=
0
. This is the third law and is the basis for absolute entropies.
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