Exercises 745has an equilibrium constant Kcnumerically equal to 1.
State whether each of the following is true or false, and
explain why.
(a) An equilibrium mixture must have the H 2 concentra-
tion three times that of N 2 and the NH 3 concentration
twice that of H 2.
(b) An equilibrium mixture must have the H 2 concentra-
tion three times that of N 2.
(c) A mixture in which the H 2 concentration is three times
that of N 2 andthe NH 3 concentration is twice that of N 2
could be an equilibrium mixture.
(d) A mixture in which the concentration of each reactant
and each product is 1 Mis an equilibrium mixture.
(e) Any mixture in which the concentrations of all reac-
tants and products are equal is an equilibrium mixture.
(f) An equilibrium mixture must have equal concentrations
of all reactants and products.
0 14.Why do we omit concentrations of pure solids and pure
liquids from equilibrium constant expressions?
0 15.Consider the following compounds, in the states indicated,
as possible reactants or products in a chemical reaction.
Which of these compounds would be omitted from the
equilibrium constant expression? H 2 O(s), H 2 O(),
H 2 O(g), HCl(g), HCl(aq), NaHCO 3 (s), N 2 (g), NH 3 (),
CO(g), and Fe 2 O 3 (s).
0 16.Consider the following compounds, in the states indicated,
as possible reactants or products in a chemical reaction.
Which of these compounds would be omitted from the
equilibrium constant expression? Explain. CaCO 3 (s),
H 2 SO 4 (), NaOH(s), NaOH(aq), O 2 (g), CH 3 COOH(),
HI(g), I 2 (s), C(graphite), and SO 3 (g).Equilibrium Constant Expression and Value of K
0 17.Write the expression for Kcfor each of the following
reactions:
(a) CO 2 (g)H 2 (g) 34 CO(g)H 2 O(g)
(b) 2NO 2 (g) 34 2NO(g)O 2 (g)
(c) 2CHCl 3 (g)3H 2 (g) 34 2CH 4 (g)3Cl 2 (g)
(d) H 2 (g)I 2 (g) 34 2HI(g)
(e) 2NOCl(g) 34 2NO(g)Cl 2 (g)
0 18.Write the expression for Kcfor each of the following
reactions:
(a) 2H 2 O(g)2SO 2 (g) 34 2H 2 S(g)3O 2 (g)
(b) 4NH 3 (g)5O 2 (g) 34 4NO(g)6H 2 O(g)
(c) PCl 3 (g)Cl 2 (g) 34 PCl 5 (g)
(d) N 2 O 4 (g) 34 2NO 2 (g)
(e) 2SO 2 (g)O 2 (g) 34 2SO 3 (g)
0 19.Write the expression for Kcfor each of the following
reactions:
(a) 2CO(g)O 2 (g) 34 2CO 2 (g)
(b) SrCO 3 (s) 34 SrO(s)CO 2 (g)
(c) 2HBr(g) 34 H 2 (g)Br 2 ()
(d) P 4 (g)3O 2 (g) 34 P 4 O 6 (s)
(e) N 2 (g)O 2 (g) 34 2NO(g)0 20.Write the expression for Kcfor each of the following
reactions:
(a) 2H 2 O 2 (g) 34 2H 2 O(g)O 2 (g)
(b) 2ZnS(s)3O 2 (g) 34 2ZnO(s)2SO 2 (g)
(c) NH 3 (g)HCl(g) 34 NH 4 Cl(s)
(d) NaF(s)H 2 SO 4 () 34 NaHSO 4 (s)HF(g)
(e) 2Cl 2 (g)2H 2 O(g) 34 4HCl(g)O 2 (g)
0 21.Write the expression for Kcfor each of the following
reactions:
(a) TlCl 3 (s) 34 TlCl(s)Cl 2 (g)
(b) CuCl 42 (aq) 34 Cu^2 (aq)4Cl(aq)
(c) 3O 2 (g) 34 2O 3 (g)
(d) 4H 3 O(aq)2Cl(aq)MnO 2 (s) 34
Mn^2 (aq)6H 2 O()Cl 2 (aq)
0 22.On the basis of the equilibrium constant values, choose the
reactions in which the productsare favored.
(a) NH 3 (aq)H 2 O() 34 NH 4 (aq)OH(aq)
K1.8 10 ^5
(b) Au(aq)2CN(aq) 34 [Au(CN) 2 ](aq)
K 2 1038
(c) PbC 2 O 4 (s) 34 Pb^2 (aq)C 2 O 42 (aq) K4.8
(d) HS(aq)H(aq) 34 H 2 S(aq) K1.0 107
0 23.On the basis of the equilibrium constant values, choose the
reactions in which the reactantsare favored.
(a) H 2 O() 34 H(aq)OH(aq)
K1.0 10 ^14
(b) [AlF 6 ]^3 (aq) 34 Al^3 (aq)6F(aq)
K 2 10 ^24
(c) Ca 3 (PO 4 ) 2 (s) 34 3Ca^2 (aq)2PO 43 (aq)
K 10 ^25
(d) 2Fe^3 (aq)3S^2 (aq) 34 Fe 2 S 3 (s)
K 1 1088
Calculation of K
0 24.The reaction between nitrogen and oxygen to form NO(g)
is represented by the chemical equation
N 2 (g)O 2 (g) 34 2NO(g)
Equilibrium concentrations of the gases at 1500 K are
1.7 10 ^3 mol/L for O 2 , 6.4 10 ^3 mol/L for N 2 , and
1.1 10 ^5 mol/L for NO. Calculate the value of Kcat
1500 K from these data.
0 25.At elevated temperatures, BrF 5 establishes the following
equilibrium.
2BrF 5 (g) 34 Br 2 (g)5F 2 (g)
The equilibrium concentrations of the gases at 1500 K
are 0.0064 mol/L for BrF 5 , 0.0018 mol/L for Br 2 , and
0.0090 mol/L for F 2. Calculate the value of Kc.
0 26.At some temperature the reaction
PCl 3 (g)Cl 2 (g) 34 PCl 5 (g)
is at equilibrium when the concentrations of PCl 3 , Cl 2 , and
PCl 5 are 10, 9, and 12 mol/L, respectively. Calculate the
value of Kcfor this reaction at that temperature.