Concise Physical Chemistry

c05 JWBS043-Rogers September 13, 2010 11:25 Printer Name: Yet to Come

PROBLEMS AND EXAMPLE 81

Cp/ T vs. T Silver(s)

T,K

0 50 100 150 200 250 300 350

C

/T, J molp

–1

0.00

0.05

0.10

0.15

0.20

0.25

FIGURE 5.2 Cp/Tvs.Tfor metallic silver Ag(s). There are no phase transitions for solid

Ag over this temperature range.

at 15 K and leads to

S 015 =

Cp

3

=

0. 67

3

= 0 .22 J K−^1 mol−^1

This small addition yieldsS 0298 = 42 .43 J K−^1 mol−^1 , which is within 0.6% of the

handbook value.

Problem 5.1

Hexa-1,3,5-triene has a boiling point of 355 K under atmospheric pressure. Estimate

the enthalpy of vaporization of hexa-1,3,5-triene.

Problem 5.2

(a) What is the entropy change brought about by heating 2.5 mol of helium from

300 to 400 K at constant volume?

(b) What is the entropy change brought about if the same heating process takes

place at constant pressure?