Chem120B
Problem Set 5
Due: February 25, 2011
1. Problems 197, 1913, 1914, and 1934 in Simon and McQuarrie’s
Physical Chemistry
.
2. We have argued several times that, in a dilute system, the number of ways to arrange
N
identical
molecules in a large volume
V
is
W
(
V
) =
V
N
×
(factors independent of volume)
Here you will use that result to calculate the entropy change
Δ
S
mix
upon mixing two dilute gases or
solutions.
(i) Consider an initial state in which
N
1
molecules of one type are confined to a region of volume
V
1
,
and
N
2
molecules of a different type are confined to a separate region of volume
V
2
. Calculate the
entropy of this state. (You may ignore contributions that are independent of volume.)
(ii) In the final state the two types of molecules are allowed to mix within the combined region of
volume
V
1
+
V
2
.
Calculate the entropy of this state (again ignoring contributions independent of
volume).
(iii) Calculate the change in entropy per molecule,
Δ
S
mix
/
(
N
1
+
N
2
)
for the specific case in which
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 Spring '09
 JAMESAMES
 Physical chemistry, Thermodynamics, Mole, pH, special material, Professor Relssieg

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