Page 92 - Modern physical chemistry

Problems 81

(4.106) with VA and VB fixed by their values at this point of tangency. The intercepts at
X B = 0 and at X B = 1 then give nwnbers VA and VB' See figure 4.5.
In place of V, one can substitute any extensive thennodynamic property. If G is such
a property, we have
[4.107]
and
G - -
-=GAXA +GBXB· [4.108]
n
A
Furthennore, the method of intercepts may be used to find G and G B •
Questions
4.1 What independent variables may be used to characterize the state of a homogeneous ther-
modynamic System?
4.2 Show that for water, the set CP, V, n) is not sufficient to characterize uniquely each macro-
scopic state.
4.3 When is a process reversible?
4.4 Define internal energy. How is this energy varied?
4.5 What is work? Give examples.
4.6 How does heat flow?
4.7 Define the conduction coefficient.
4.8 Discuss the first law of thermodynamics.
4.9 Why doesn't a system in a particular state have a definite heat content or work content?
4.10 Define enthalpy.
4.11 What does the PV term in the enthalpy represent?
4.12 What does the vanishing of CaE/aV)T imply about the interactions between the molecules of
a given system?
4.13 How are Cp and Cv related when the system is an ideal gas?
4.14 When is a process nearly adiabatic?
4.15 Derive the equation for the speed of sound in an ideal gas.
4.16 Discuss the contributions to the energy capacity Cv '
4.17 How does a partical derivative differ from an ordinary derivative?
4.18 Why is CaE/aV)T called the internal pressure in a system?
4.19 How is cap/any related to the coefficients of cubical expansion and compressibility?
4.20 How is an exact differential different from an inexact one? Give physical examples of each.
4.21 How is a partial molar property defined? Give an example.
4.22 Why are VA and VB constant at a given temperature, pressure, and concentration?

Problems
4.1 How much work is done on the surroundings when 0.86 mol Zn reacts with an acid to
produce hydrogen at 25° C?
4.2 Calculate the work done on the surroundings when 1.35 mol water is decomposed by elec-
trolysis at 1.00 atm and 25° C.
4.3 Calculate w when 100 g argon is heated from 25° to 75° C at 1.00 atm.
4.4 1f 1.00 mole ideal gas travels down a tube at 2.00 atm pressure and 25° C, meets and passes
through a porous plug, and emerges at 1.00 atm pressure and 25° C, what is w?
4.5 From a large volume of liquid benzene, 0.800 mol is vaporized at 80.1 ° C and 1.000 atm, the
boiling point, where the heat of vaporization is 393.7 J g-l . Calculate Ca) q, (b) w, Cc) M1,
Cd) !lE.
4.6 The pressure on 1.00 mol helium is reduced reversibly at 25° C from 10.0 atm to 1.00 atm.
Calculate Ca) q, (b) w, Cc) M1, Cd) M.