South Pasadena • Honors Chemistry
Name
8 • Equilibrium
Period
8.2
PROBLEMS
–
1. Consider the reaction:
EQUILIBRIUM
SO2Cl2 (g)  SO2 (g) + Cl2 (g)
Initially, 0.10 mol NO, 0.050 mol H2, and 0.10 mol
H2O are placed in a 1.0 L container at 300 K. At
equilibrium, [NO] = 0.062 M. What are
concentrations of all substances at equilibrium?
What is the value of Keq?
When 2.00 mol of SO2Cl2 is placed in a 2.00 L
flask at 303 K, 56% of the SO2Cl2 decomposes to
SO2 and Cl2. What are concentrations of all
substances at equilibrium? What is the value of
Keq?
SO2Cl2 (g)  SO2 (g) + Cl2 (g)
2 NO (g) + 2 H2 (g)  N2 (g) + 2 H2O (g)
0.10 M
Change
Equil.
0.050 M
0M
0.012 M
0.019 M
2
Keq =
0.10 M
Initial
1.00 M
0M
0M
+0.038
Change
‒0.56 M
+0.56 M
+0.56 M
0.138 M
Equil.
0.44 M
0.56 M
0.56 M
‒0.038 M ‒0.038 M +0.019 M
0.062 M
PROBLEMS
3. Consider the reaction:
2 NO (g) + 2 H2 (g)  N2 (g) + 2 H2O (g)
Initial
Date
2
[N2][H2O]
(0.019)(0.138)
=
= 654
[NO]2[H2]2 (0.062)2(0.012)2
Keq =
[SO2][Cl2] (0.56)(0.56)
=
= 0.713
[SO2Cl2]
(0.44)
2. Consider the reaction:
2 SO3 (g)  2 SO2 (g) + O2 (g)
At a particular temperature, 12.0 mol SO3 is placed
into a 3.0 L container. At equilibrium, 3.0 mol SO2
is present. What is the value of Keq?
2 SO3 (g)  2 SO2 (g) + O2 (g)
Initial
4.0 M
0M
0M
Change
‒1.0 M
+1.0 M
+0.50 M
Equil.
3.0 M
1.0 M
0.50 M
Keq =
[SO2]2[O2] (1.0)2(0.50)
=
=0.056
[SO3]2
(3.0)2
4. Consider the reaction:
N2O4 (g)  2 NO2 (g)
Keq = 0.513 at 500 K
The reaction vessel initially contains 0.0500 M N2O4. What are concentrations of all substances at
equilibrium?
N2O4 (g)  2 NO2 (g)
Initial
0.0500 M
0M
Change
‒x
+2x
Equil.
0.0500 ‒ x
2x
Keq =
[NO2]2
(2x)2
=
= 0.513
[N2O4] (0.0500 ‒ x)
x = 0.0385 (use quadratic formula)
[N2O4]eq = 0.0115 M, [NO2]eq = 0.0770 M
5. Consider the reaction:
2 NO (g)  N2 (g) + O2 (g)
Keq = 2400 at 2000°C
The initial concentration of NO is 0.200 M. What are concentrations of all substances at equilibrium?
2 NO (g)  N2 (g) + O2 (g)
Keq =
Initial
0.200 M
0M
0M
Change
‒2x
+x
+x
Equil.
0.200 ‒ 2x
x
x
[N2][O2]
(x)(x)
=
= 2400
[NO]2
(0.200 ‒ 2x)2
x = 0.0990 (square root both sides)
[NO]eq = 0.00202 M, [N2]eq = [O2]eq = 0.0990 M
6. Consider the reaction:
NiO (s) + CO (g)  Ni (s) + CO2 (g)
Keq = 4000 at 1500 K
A mixture of solid nickel(II) oxide and 0.20 M carbon monoxide is placed in a container and allowed to come
to equilibrium. What are concentrations of all substances at equilibrium?
NiO (s) + CO (g)  Ni (s) + CO2 (g)
Initial
0.20 M
0M
Change
‒x
+x
Equil.
0.20 ‒ x
x
Keq =
[CO2]
x
=
= 4000
[CO] 0.20 ‒ x
x = 0.20 M
[CO2]eq = 0.20 M, [CO]eq = 5.0 × 10‒5 M
7. Consider the reaction:
CO (g) + H2O (g)  CO2 (g) + H2 (g)
Keq = 102 at 500 K
A reaction mixture initially contains 0.110 M CO and 0.110 M H2O. What are concentrations of all
substances at equilibrium?
CO (g) + H2O (g)  CO2 (g) + H2 (g)
Initial
Change
Equil.
0.110 M 0.110 M
‒x
0M
0M
+x
+x
X
x
‒x
0.110 ‒ x 0.110 ‒ x
Keq =
[CO2][H2]
(x)(x)
=
= 102
[CO][H2O] (0.110 ‒ x)(0.110 ‒ x)
x = 0.100 M
(square root both sides)
[CO]eq = 0.010 M, [H2O]eq = 0.0100 M,
[CO2]eq = 0.100 M , [H2]eq = 0.100 M
8. Consider the reaction:
H2 (g) + F2 (g)  2 HF (g)
Keq = 1.15 × 102
If 3.00 mol of H2, 3.00 mol of F2, and 3.00 mol of HF were placed in a 1.50 L container, what are
concentrations of all substances at equilibrium?
H2 (g) + F2 (g)  2 HF (g)
Initial
2.00 M
2.00 M
2.00 M
Change
‒x
‒x
+2x
Equil.
2.00 ‒ x
2.00 ‒ x
2.00 + 2x
[H2]eq = [F2]eq = 0.47 M, [HF]eq = 5.06 M
Q=
[HF]2
(2.00)2
=
= 1 < 115
[H2][F2] (2.00)(2.00)
Keq =
Q < Keq
[HF]2
(2.00 + 2x)2
=
= 115
[H2][F2] (2.00 ‒ x)(2.00 ‒ x)
x = 1.53
M
9. Consider the reaction: HC2H3O2 (aq) + H2O (ℓ)  H3O+ (aq) + C2H3O2‒ (aq) Keq = 1.8 × 10‒5 at 25°C
A solution initially contains 0.210 M HC2H3O2. What are concentrations of all substances at equilibrium?
HC2H3O2 + H2O  H3O+ + C2H3O2‒
Initial
0.210 M
0M
0M
Change
‒x
+x
+x
Equil.
0.210 ‒ x
X
x
[H3O+][C2H3O2‒]
(x)(x)
=
≈
[ HC2H3O2]
0.210 ‒ x
x2
= 1.8 × 10‒5
0.210
(Assume x << 0.210 so 0.210 ‒ x ≈ 0.210)
Keq =
x = 0.00194 M
[H3O+]eq = [C2H3O2‒]eq = 0.00194 M,
[HC2H3O2]eq = 0.0208 M
10. Consider the reaction:
SO2Cl2 (g)  SO2 (g) + Cl2 (g)
Keq = 2.99 × 10‒7 at 227°C
A reaction mixture initially contains 0.175 M SO2Cl2. What are concentrations of all substances at
equilibrium?
SO2Cl2 (g)  SO2 (g) + Cl2 (g)
Initial
0.175 M
0M
0M
Change
‒x
+x
+x
Equil.
0.175 ‒ x
x
x
Keq =
[SO2][Cl2]
(x)(x)
=
[SO2Cl2] (0.175 ‒ x)
x2
= 2.99 × 10‒7
0.175
(Assume x << 0.175 so 0.175 ‒ x ≈ 0.175)
x = 2.29 × 10‒4 M
[SO2]eq = [Cl2]eq = 2.29 × 10‒4 M,
[SO2Cl2]eq = 0.175 M