Concise Physical Chemistry

c06 JWBS043-Rogers September 13, 2010 11:25 Printer Name: Yet to Come

PROBLEMS AND EXAMPLE 91

(c) Show thatdU=TdS−pdV.

(d) Combine (a), (b), and (c) to show that

dG=Vdp−SdT

Problem 6.2

(a) Calculate the change in Gibbs free energy that takes place with the isothermal

compression of water treated as an incompressible liquid at 298 K from 1.00

to 2.00 bars pressure.

(b) Calculate the change in Gibbs free energy that takes place with the isothermal

compression of water treated as an ideal gas at 298 K from 1.00 to 2.00 bars

pressure.

(c) Comment upon the difference.

Problem 6.3

The statement has been made: “Algebraic manipulation gives

dG=Vdp−SdT”

Prove this statement.

Problem 6.4

A chemical reaction at 1.0 bar pressure has
G^298 r,p= 1 =−335 kJ mol−^1. The Gibbs

function of the reactant system changes by 7.5 kJ mol−^1 when the pressure is changed

from 1.0 bar to p 2. The product system changes by 8.4 kJ mol−^1 over the same pressure

change. What is
G^298 r,p 2?

Problem 6.5

What is the entropy change of a Trouton’s rule liquid at its boiling point?

Problem 6.6

The heat capacity of carbon disulfide CS 2 (s) is 6.9 J K−^1 mol−^1 at 15.0 K. What is its

standard entropy at 15.0 K, assuming that the solid is a perfect crystal.

Problem 6.7

Solid carbon disulfide shows the following experimental values of heat capacity as a

function of temperature. Taking the Debye contribution into account (Problem 6.4),

find the standard entropy of CS 2 (s) at its normal melting point of 161 K.