The Richard Stockton College of New Jersey
Chemistry Program, School of Natural Sciences and Mathematics
PO Box 195, Pomoma, NJ
CHEM 3410: Physical Chemistry I — Fall 2008
In-class Practice Problems
September 19, 2007
1. One mole of an ideal gas, with Cv=3
2R, is heated (a) at constant pressure and (b) at constant
volume, from 298 K to 353 K. Calculate ∆Sfor the system in each case.
2. The standard entropy of Pb(s) at 298.15 K is 64.80 J/mol·K. Assume the heat capacity of Pb(s) is
given by:
Cp(P b, s) = 22.13 + 0.01172T+ 1.00 ×10−5T2
The melting point of lead is 327.4◦C and the heat of fusion under these conditions is 4770 J/mol.
Assume the heat capacity of liquid lead is given by:
Cp(P b, l) = 32.51 −0.00301T
(a) Calculate the standard entropy of Pb(l) at 500◦C.
(b) Calculate ∆Hfor the transformation Pb(s, 25◦C) to Pb(l, 500◦C).
3. At 100◦C 200 g of mercuty are added to 100 g of water at 20 ◦C. The specific heat capacities of
water and mercury may be taken as constant at 4.18 and 0.140 J/K·g, respectively. Calculate the
entropy change of
(a) the mercury
(b) the water
(c) the system
4. One mole of H2O(l) is supercooled to -2.25◦C at 1 bar pressure. The freezing temperature of water
at this pressure is 0.00◦C. The transformation H2O(l) →H2O(s) is suddenly observed to occur.
By calculating ∆S, ∆Ssurroundings and ∆Stotal , verify that this transformation is spontaneous at
-2.25◦C.
The heat capacities are given by Cp(H2O(l)) = 75.3 J K−1mol−1and CP(H2O(s))= 37.7 J K−1mol−1,
and ∆Hfusion = 6.008 kJ mol1at 0.00◦C. Assume that the surroundings are at -2.25◦C.
[Hint: Consider the two pathways at 1 bar: (a) H2O(l, -2.25◦C) →H2O(s, -2.25◦C) and (b)
H2O(l, −2.25◦C) →H2O(l, 0.00◦C) →H2O(s, 0.00◦C) →H2O(s, -2.25◦C). Because Sis a state
function, ∆Smust be the same for both pathways.]