Page 176 - Modern physical chemistry

168 Relationships among Reactants

7.19 Show that for a condensed phase at absolute zero (aSrdT)v vanishes.
7.20 Calculate the entropy correction for gas imperfection of benzene at 400 K and 1.000 atm.
7.21 Molecules 36CI36CI and 37CI37CI need only be rotated by 180° to obtain a configuration indis-
tinguishable from the original one, while 36CI37CI must be rotated by a full 360° . Thus, the
latter has twice as many disjoint configurations as either of the former molecules. Deter-
mine the resulting state number ratio W IW 1 for the reaction

.!. 35 C1 2 (g) +.!.37 C1 2 (g)~35C137 Cl (g).
2 2
Then calculate ~ and finally LlGo at 25° C.
7.22 At 500 K the log Kr for H 20 (g) is 22.891 and for HCI (g) 10.150, while at 600 K these numbers
are 18.637 and 8.530 respectively. Calculate Kp and Kc at these temperatures for the reaction
1
2HCL (g) + - O2 (g) E ) H20 (g) + C12 (g).
2
7.23 Show how unit pressure enters equation (7.40) to make it correct dimensionally. How does
unit activity enter equation (7.42)?
7.24 At 50° C, Kp for

is 4.000 X 10-4 bar and Kp for
1 1
-CUS04 ·5H20 (8) E ) -CUS04· 3H20 (8) + H20 (g)
2 2
is 6.049 X 10- 2 bar. What is the pressure of CO 2 in the vapor at equilibrium with NaHC03 (s),
N~C03 (s), CuS0 4 5H 20 (s), and CuS0 4 3H 20 (s) at 50° C?
7.25 If solid ammonium carbamate and solid ammonium hydrosulfide are both vaporized into a
vacuum, what are the partial pressures when equilibrium is set up with the solids at 20° C,
where Kpfor

NH4 COONH2 (8) E ) 2NH3 (g) + CO2 (g)

is 8.09 x 10-0 bar and Kp for

is 5.62 X 10- 2 bar?
7.26 From the numbers in problem 7.22, calculate ~ 550 K for the given reaction.
at
7.27 For the equilibrium
CO (g) + 2H2 (g) E ) CH3 0H (g)
at 250° C and 170 atm, expression Kp equals 2.1 x 10- 2 atm- 2 • If under these conditions,
Yco = 1.09, YH:! = 1.06, and YCHa0H = 0.45, what is eqUilibrium constant Kfor the reaction?

References
Books
Barin, I.: 1989, Thermochemical Data oj Pure Substances, Parts I and II, VCH, Weinheim, pp. I:
1-37, 1-1739
In the introduction, Barin surveys the basic thermodynamic principles and equations. The
tables are then described. Representative examples of their use are developed.