Basic Chemical Thermodynamics - Elements of Environmental Engineering: Thermodynamics and Kinetics - page 41

11. If Δ H > 0, the reaction is always possible.
12. Although S sys may increase, decrease, or remain constant, S univ
cannot decrease.
2.28 2 The molar Gibbs free energy for CO 2 in the gas phase is − 394.4 kJ/mol
and that in water is − 386.2 kJ/mol. Is the dissolution of CO 2 a spontaneous
process at 298 K and 1 atm total pressure?
2.29 1 What pressure is required to boil water at 393 K? The heat of vaporization
of water is 40.6 kJ/mol.
2.30 2 What is the pH of pure water at 37 ◦ C? For the reaction H 2 O H + +
OH − , K eq is 1 × 10 − 14 M 2 at 25 ◦ C and the enthalpy of dissociation is
55.8 kJ/mol.
2.31 3 A human being is an open system and maintains a constant body tem-
perature of 310 K by removing excess heat via evaporation of water
through the skin. Consider a person weighing 175 pounds capable of
generating heat by digesting 100 mol of glucose through the reaction
C 6 H 12 O 6 ( s ) + 6O 2 ( g ) → 6CO 2 ( g ) + 6H 2 O(l). How much water will
have to be evaporated to maintain the body temperature at 310 K? The
C p for water is 33.6 J/K mol. For water, Δ H v = 40.5 kJ/mol. The ambient

temperature is 298 K.
2.32 3 A fundamental energy-giving reaction for the creation of the pri-
mordial living cell is proposed to be the formation of iron pyrites
by the reaction FeS ( s ) + H 2 S ( aq ) 6FeS 2 ( s ) + 2H + ( aq ) + 2e − (aq). The
energy released by this reaction is used to break up CO 2 and
form the carbon compounds essential to life. Estimate the max-
imum work obtainable from the above reaction under standard
conditions.
2.33 2 For a hurricane (Figure 2.2) follow Example 2.2 to derive the maximum
wind velocity predicted from theory. The specific enthalpy of air under
moist conditions is given by C p ,a t + (C p ,w t + h w,e )x w , where C p ,a =
1.006 kJ/kg ◦ C and C p ,w = 1.84 kJ/kg ◦ C are, respectively, the specific
heat capacity of air and water. The water content of moist air is x w =
0.0203 kJ/kg. Temperature t is given in ◦ C and enthalpy of water evapo-
ration h w,e =

2520 kJ/kg. The surface temperature of air in contact with
warm, moist water can be taken to be 27 ◦ C, while that of ambient dry air
is 23 ◦ C. Give the answer for velocity in miles per hour.

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