The Foundations of Chemistry

Exercises 751

Calculate KPand Kcfor the reaction at 400°C and at

800°C.

0 95.Kc19.9 for the reaction

Cl 2 (g)F 2 (g) 34 2ClF(g)

What will happen in a reaction mixture originally

containing [Cl 2 ]0.200 mol/L, [F 2 ]0.300 mol/L, and

[ClF]0.950 mol/L?

0 96.A mixture of CO, H 2 , CH 4 , and H 2 O is kept at 1133 K

until the reaction

CO(g)3H 2 (g) 34 CH 4 (g)H 2 O(g)

has come to equilibrium. The volume of the container is

0.100 L. The equilibrium mixture contains 1.21 10 ^4 mol

CO, 2.47 10 ^4 mol H 2 , 1.21 10 ^4 mol CH 4 , and 5.63

 10 ^8 mol H 2 O. Calculate KPfor this reaction at 1133 K.

0 97.What would the pressure of hydrogen be at equilibrium

when PWCl 6 0.012 atm and PHCl0.10 atm? KP

1.37 1021 at 900 K.

WCl 6 (g)3H 2 (g) 34 W(s)6HCl(g)

CONCEPTUAL EXERCISES

0 98.What is the relationship between the forward and reverse

reactions in an equilibrium?

0 99.The term “equilibrium” brings to mind the word “equal.”

What is the relationship between the two terms?

100.The masses of participants in a chemical equilibrium are

not the same on both sides of the reaction. Does the equi-

librium concept violate the Law of Conservation of

Matter? Explain.

101.A sample of benzoic acid, a solid carbon-containing acid,

is in equilibrium with an aqueous solution of benzoic acid.

A tiny quantity of D 2 O, water containing the isotope^2 H,

deuterium, is added to the solution. The solution is allowed

to stand at constant temperature for several hours, after

which some of the solid benzoic acid is removed and ana-

lyzed. The benzoic acid is found to contain a tiny quantity

of deuterium, D, and the formula of the deuterium-

containing molecules is C 6 H 5 COOD. Explain how this

can happen.

102.Imagine yourself the size of atoms and molecules inside a

beaker containing the following equilibrium mixture with

a Kgreater than 1.

[Co(OH 2 ) 6 ]^2 (aq)4Cl(aq) 34

pink CoCl 42 (aq)6H 2 O(
)

blue

Write a brief description of what you observe around you

before and after additional water is added to the mixture.

BUILDING YOUR KNOWLEDGE

103.Hemoglobin, Hb, has four Fe atoms per molecule that, on

the average, pick up roughly three molecules of O 2.

Hb(aq)3O 2 (g) 34 Hb(O 2 ) 3 (aq)

Discuss mountain or space sickness in terms of this equi-

librium.

Astronauts incur the risk of space sickness.

104.At room temperature, the equilibrium constant for the

reaction

2SO 2 O 234 2SO 3

is 6.98 1024. Calculate 
G^0 rxn and 
Gf^0 (SO 3 ), given

the additional information that 
Gf^0 (SO 2 )

300.194 kJ/mol. Check your answer by looking up


Gf^0 (SO 3 ) in Appendix K.

105.At 25°C, 550.0 g of deuterium oxide, D 2 O (20.0 g/mol;

density 1.10 g/mL), and 498.5 g of H 2 O (18.0 g/mol; den-

sity 0.997 g/mL) are mixed. The volumes are additive.

47.0% of the H 2 O reacts to form HDO. Calculate Kcat

25°C for the reaction

H 2 OD 2 O 34 2HDO

106.At its normal boiling point of 100°C, the heat of vapor-

ization of water is 40.66 kJ/mol. What is the equilibrium

vapor pressure of water at 50°C? (You may wish to review

Example 15-20.)

107.Use the data in the preceding exercise to calculate the tem-

perature at which the vapor pressure of water is 1.50 atm.