Basic Chemical Thermodynamics - Elements of Environmental Engineering: Thermodynamics and Kinetics - page 40

water?Assume that both the air and water remain at a constant temperature
of 308 K. The heat of vaporization of liquid water at 308 K is 2425 kJ/kg.
2.23 3 The predominant form of CaCO 3 in nature is calcite. Marine shells are
made up of this form of calcium carbonate. However, there also exists
anotherformofCaCO 3 ,calledaragonite.Theydifferinpropertiesat298 K
as follows:

Property Calcite Aragonite

Standard free energy of
formation (kJ/mol) − 1128.7 − 1127.7

Density (g/cm 3 )

2.71 2.93

(a) Is the conversion of calcite to aragonite spontaneous at 298 K?
(b) At what pressure will the conversion be spontaneous at 298 K?
2.24 3 Municipal landfills contain refuse that are continually decomposed by
indigenous bacteria. This produces large quantities of methane gas. Let us
consider a large landfill that contains approximately 10 10 m 3 of methane.
Is it possible that this landfill gas, by being allowed to expand and cool to
ambient conditions (without combustion), can be used to produce power?
In other words, you are asked to determine the useful work that can be
obtained. Assume the following: the heat capacity at constant pressure is
36 J/mol K, pressure in the landfill is 8 atm, and temperature in the landfill
is 240 ◦ C. The molecular weight of methane is 0.016 kg/mol.
2.25 2 Methyl mercury (CH 3 ) 2 Hg is the most easily assimilable form of mercury
by humans. It is present in both air and water in many parts of the United
Statesandtheworld.Considerthefollowingprocessbywhichitconvertsto
elemental Hg: (CH 3 ) 2 Hg → C 2 H 6 + Hg. Is the reaction favorable under
ambient conditions? Look up the Δ G f for the compounds in appropriate
references.
2.26 2 For the reaction H 2 S(g) → H 2 S(aq), the enthalpy of dissolution is
− 19.2 kJ/mol at 298 K. If the temperature is raised to 318 K, by how
much will the equilibrium constant of the reaction increase?
2.27 1 State whether the following statements are true or false:
1. The surface temperature in Baton Rouge was 94 ◦ F, and 500 m above
the temperature was 70 ◦ F on September 5, 1997. The atmosphere is
stable.
2. Surface tension can be expressed in Pa/m 2 .
3. The entropy of an ideal gas is only a function of temperature.
4. The first law requires that the total energy of a system can be
conserved within the system.
5. The entropy of an isolated system must be a constant.
6. The C p of an ideal gas is independent of P .
7. Heat is always given by the integral of T d S .
8. Chemical potential is an extensive property.
9. For an adiabatic process, d U and δ w are not equal.
10. The heat of reaction can be obtained from the heats of formation of
reactants and products.