Concise Physical Chemistry

c07 JWBS043-Rogers September 13, 2010 11:25 Printer Name: Yet to Come

106 EQUILIBRIUM

pressure of N 2 O 4 (g) had dropped to 1.975 bar. What isKeqfor this reaction? Compare

your answer to the calculated value (Section 7.2). What are the units ofKeq?

Problem 7.3

Supposing that a simple A(g)→←B(g) reaction has an equilibrium constantKeq=

0 .100 atT=200 K andKeq′ = 0 .200 atT=300 K. What is
rH◦for the reaction?

Problem 7.4

For the reaction

Br 2 (g)→2Br(g)

the equilibrium constant has been measured and found to be 0.410 at 1125 K and

1.40 at 1175 K. What isKeqat 1225 K?

Problem 7.5

Data quoted in Lewis and Randall (1961) for the formation reaction of H 2 S

H 2 (g)+^12 S 2 (g)=H 2 S(g)

include the values given in Table 7.1.

TABLE 7.1 T,1/T,K,andlnKfor formation of H 2 Sfromitselements.

T 1023 1218 1405 1667

1 /T 9. 775 × 10 −^48. 210 × 10 −^47. 117 × 10 −^45. 999 × 10 −^4

K 105.9 20.18 6.209 1.807

lnK 4.662 3.005 1.826 0.5917

What is
rH◦for this reaction? What is
rS◦?

Problem 7.6

A reaction in the gas phase hasKeq=10 at 298 K and 10−^1 at 500 K. Is the reaction

endothermic or exothermic? Explain this in terms of Le Chatelier’s principle.

Problem 7.7

An experiment was set up so that conditions (pH, pMg+, ionic strength, etc.) were

identical to those described in Exercises 7.1 and 7.2, except that, in this experiment,