CHEM 1215 -- Unit 4 Practice Problems
1. Write the equilibrium
constant expressions (Kc) for the following reactions.
a. 
2 SO2 (g) + O2
(g) 2 SO3 (g)
b. 
FeO (s) + H2 (g) Fe (s) + H2O (g)
2. Write the equilibrium
constant expression (Kp) for reaction (a)
in question 1.
3.
At equilibrium, the
reaction N2(g) + 3H2(g) 2NH3(g) had the following
concentrations: [N2] = 0.0850
M, [H2] = 3.10 x 10-3 M, and [NH3] = 0.0310
M. What is the value of Kc ?
4. Write the solubility
product constant expression for the disoolution of chromium (III) hydroxide.
5. Silver sulfate
dissolves according to the following process:
Ag2SO4
(s) 2 Ag+
(aq) + SO42-
(aq) Ksp = 1.5 x 10-5
What are the equilibrium concentrations of Ag+
(aq) and SO42- (aq) if a sample of silver sulfate is
added to water?
6. Sulfur trioxide
decomposes at high temperature in a sealed container:
2 SO3 (g) 2 SO2 (g) + O2
(g)
Initially,
the vessel is charged at 1000K with SO3 (g) at a concentration of
6.09 x 10-3 M. At
equilibrium, the SO3 concentration is 2.44 x 10-3 M.
a. What
are the equilibrium concentrations of SO2 and O2?
b.
What is the value of Kc at 1000 K?
7. 
The Kp at 450oC
for the equilibrium: N2(g)
+ 3 H2 (g) 2 NH3
(g) is 4.51 x 10-5.
a. If 105 atm NH3 (g),
35 atm N2 (g), and 495 atm H2 (g) are present in a
reactor, calculate the reaction quotient, Q.
b. Is the system at
equilibrium? If not, which direction
must the mixture shift in order to achieve equilibrium?
c. What is the value of Kp for the reaction NH3 (g) N2 (g) + 3 H2
(g)?
8. 
A 2.000 L reactor is filled with
1.000 mol H2 (g) and 2.00 mol I2 (g) at 448oC. The value of the rate constant, Kc,
for the reaction H2
(g) + I2 (g) 2 HI
(g) at 448oC is 50.5.
What are the concentrations of H2, I2, and HI at
equilibrium?
9. Given the reaction NO (g) + O3
(g) NO2 (g) + O2
(g) H = -199 kJ, what happens
when:
a. NO is added?
b. NO2 is
added?
c. The volume of the
container is doubled?
d. The reaction is
heated?
e. O3 is
removed?
f.
NO2 is removed?
g. Ar (g) is added to
increase the total pressure?
h. Powdered nickel is
added as a catalyst?
10.
A student measured the
equilibrium constant for the formation of [Fe(SCN)]2+
from Fe3+ and SCN-.
In one experiment a solution prepared by mixing 5.00 mL of 0.00800
M Fe(NO3)3, 10.0 mL of 0.00400 M KSCN, and 5.00 mL of
0.500 M HNO3 contained 4.83 x 10-4 M [Fe(SCN)]2+
at equilibrium. Calculate the equilibrium
constant for the reaction.
11. What is the [H+]
for a pH 6.25 solution?
12. What are the [H+],
[OH-], pH, and pOH for a 1.65 x 10-4 M HCl?
13. What are the [H+],
[OH-], pH, and pOH for a 2.40 x 10-5 M Ca(OH)2?
14. What is the pH of a
solution prepared by mixing 10.0 mL of 2.40 x 10-6 M Ca(OH)2 and 15.0 mL of 2.50 x 10-5 M
KOH?
15. What are the [H+],
[OH-], pH, and pOH for a 0.200 M HC7H5O2
solution?
(Ka = 6.3 x 10-5)
16. What are the [H+],
[OH-], pH, and pOH for a 0.200 M NH2OH solution?
(Kb = 1.1 x 10-8)
17. Identify the
Bronsted-Lowry acid and base and their conjugates:
NH2OH + C5H5NH+
à NH3OH+ + C5H5N
18. Calculate the pH of a
buffer when sodium hydrogen sulfate has a concentration of 0.100 M and sodium
sulfate has a concentration of 0.230 M (Ka of hydrogen sulfate ion
= 1.2 x 10-2).
19. Calculate the pH of a
buffer prepared by mixing 25.0 mL of 0.15 M sodium hydrogen sulfate and 35.0 mL
of 0.25 M sodium sulfate.
20. Calculate the acid to
base ratio needed to make a pH 3.80 buffer from acetic acid
(Ka = 1.8 x 10-5) and
sodium acetate.
21. What is the pH at the
equivalence point when 25.0 mL of 0.125 M HCl reacts with 0.150 M NaOH?
22. Calculate the pH at
the equivalence point when 25.0 mL of 0.140 M HClO
(Ka
= 3.0 x 10-8) is titrated with 0.200 M NaOH.
23. How many mL of 0.125 M
sodium carbonate are needed to react completely with 12.0 mL of 0.150 M
phosphoric acid?
24. Calculate the
concentration of a sulfuric acid solution if 25.0 mL of sulfuric acid was needed
to neutralize 1.85 g of solid aluminum hydroxide.