Chem 1A (Kunkel ) – Practice Final
1. Consider a solution of 2.0 M HCN and 1.0 M NaCN (Ka for HCN = 6.2 × 10–10).
Which of the following statements is true?
A) The solution is not a buffer because [HCN] is not equal to [CN–].
B) The pH will be below 7.00 because the concentration of the acid is greater than that
of the base.
C) [OH–] > [H+]
D) The buffer will be more resistant to pH changes from addition of strong acid than to
pH changes from addition of strong base.
E) All of these statements are false.
2. Which of the following will not produce a buffer solution?
A) 100 mL of 0.1 M NaF and 50 mL of 0.1 M HCl
B) 100 mL of 0.1 M NaF and 25 mL of 0.2 M HCl
C) 100 mL of 0.1 M NaF and 75 mL of 0.2 M HCl
D) 50 mL of 0.2 M NaF and 5 mL of 1.0 M HCl
E) All of these result in a buffer solution
3. Calculate the pH of a solution prepared by mixing 50 mL of a 0.10 M solution of HF
with 25 mL of a 0.20 M solution of NaF. pKa of HF is 3.14.
A) 3.14 B) 10.80 C) 5.83 D) 7.35 E) 12.00
4. What combination of substances will give a buffered solution that has a pH of
5.05? Assume each pair of substances is dissolved in 5.0 L of water. (Kb for NH3 = 1.8
× 10–5; Kb for C5H5N = 1.7 × 10–9)
A) 1.0 mol NH3 and 1.5 mol NH4Cl
B) 1.5 mol NH3 and 1.0 mol NH4Cl
C) 1.0 mol C5H5N and 1.5 mol C5H5NHCl
D) 1.5 mol C5H5N and 1.0 mol C5H5NHCl
E) none of these
5. How much solid NaCN must be added to 1.0 L of a 0.5 M HCN solution to produce
a solution with pH 7.0? Ka = 6.2 × 10–10 for HCN.
A) 0.0034 g B) 11 g C) 160 g D) 24 g E) 0.15 g
6. For 105.0 mL of a buffer that is 0.40 M in HOCl and 0.36 M in NaOCl, what is the
pH after 13.4 mL of 1.5 M NaOH is added? Ka for HOCl = 3.5 × 10–8. (Assume the
volumes are additive.)
A) 7.03 B) 6.91 C) 7.41 D) 7.50 E) 7.88
7. The pH at the equivalence point of a titration of a weak acid with a strong base is
A) less than 7.00.
B) equal to 7.00.
C) greater than 7.00.
D) More data are needed to answer this question.
8. A 74.0 mL sample of 0.13 M HNO2 (Ka = 4.0 × 10–4) is titrated with 0.14 M NaOH.
What is the pH after 25.8 mL of NaOH has been added?
A) 7.00 B) 10.38 C) 3.62 D) 3.18 E) 2.97
9. A 100. mL sample of 0.10 M HCl is mixed with 50. mL of 0.10 M NH3. What is the
resulting pH? (Kb for NH3 = 1.8 × 10–5)
A) 12.52 B) 3.87 C) 1.30 D) 7.85 E) 1.48
10. After adding 25.0 mL of 0.100 M NaOH to 100.0 mL of 0.100 M weak acid (HA),
the pH is found to be 5.90. Determine the value of Ka for the acid HA.
A) 1.6 × 10-11 B) 4.2 × 10-7 C) 2.1 × 10-5 D) 3.5 × 10-9 E) none of these
11. A 100.0 mL sample of 0.2 M (CH3)3N (Kb = 5.3 × 10–5) is titrated with 0.2 M HCl.
What is the pH at the equivalence point?
A) 9.9 B) 3.1 C) 10.3 D) 5.4 E) 7.0
12. Which of the following compounds has the lowest solubility, in moles per liter, in
water?
A) Al(OH)3 Ksp = 2 × 10–32
B) CdS Ksp = 1.0 × 10–28
C) PbSO4 Ksp = 1.3 × 10–8
D) Sn(OH)2 Ksp = 3 × 10–27
E) MgC2O4 Ksp = 8.6 × 10–5
13. Which is the correct mathematical expression for the molar solubility (s) in moles
per liter of Fe3(PO4)2?
A) 6s2 B) 12s3 C) 6s5 D) 108s5 E) 5s6
14. It is observed that 7.5 mmol of BaF2 will dissolve in 1.0 L of water. Use these data
to calculate the value of Ksp for barium fluoride.
A) 7.5 × 10–3 B) 4.2 × 10–7 C) 1.7 × 10–6 D) 5.6 × 10–5 E) 2.1 × 10–12
15. Calculate the solubility of Cu(OH)2 in a solution buffered at pH = 8.50. (Ksp = 1.6 ×
10–19)
A) 1.6 × 10–2 M B) 1.8 × 10–7 M C) 1.6 × 10–8 M D) 5.7 × 10–10 M E) none of these
16. Calculate the solubility of Ag2SO4 [Ksp = 1.2 × 10–5] in a 2.0 M AgNO3 solution.
A) 1.4 × 10–2 M B) 3.0 × 10–6 M C) 1.2 × 10–5 M D) 6.0 × 10–6 M E) none of these
17. Identify the Brønsted acids and bases in the following equation (A = Brønsted
acid, B = Brønsted base).
HPO42- +
HSO4-  H2PO4- +
SO42A)
B
A
B
A
B)
B
B
A
A
C)
A
B
A
B
D)
A
B
B
A
E)
B
A
A
B
18. The acids HC2H3O2 and HF are both weak, but HF is a stronger acid than
HC2H3O2. HCl is a strong acid.
Order the following according to base strength.
A) C2H3O2– > F– > Cl– > H2O
B) C2H3O2– > F– > H2O > Cl–
C) Cl– > F– > C2H3O2– > H2O
D) F– > C2H3O2– > H2O > Cl–
E) none of these
19. For nitrous acid, HNO2, Ka = 4.0 × 10–4. Calculate the pH of 0.33 M HNO2.
A) 1.94 B) 0.48 C) 2.92 D) 4.36 E) 3.40
20. The pH of a 0.6 M solution of a weak acid is 4.0. What percent of the acid has
ionized?
A) 0.02% B) 2% C) 7% D) 4% E) 0.06%
21. If, at a given temperature, the equilibrium constant for the reaction
H2 (g) + Cl2 (g)  2HCl (g) is 6.0, then the equilibrium constant for the reaction
HCl (g)  1/2 H2 (g) + 1/2 Cl 2 (g) can be represented as
A) 6.0 B) 36 C) 0.41 D) 0.17 E) 0.028
22. For the reaction below, Kp = 1.16 at 800.°C.
CaCO3 (s) CaO (s) + CO2 (g)
If a 25.0 g sample of CaCO3 is put into a 10.2 L container and heated to 800.°C, what
percent of the CaCO3 will react to reach equilibrium?
A) 23.7% B) 53.8% C) 13.4% D) 100.% E) 47.4%
23. Consider the reaction 2NOBr(g)  2NO(g) + Br2 (g)
A 1.0 L vessel was initially filled with pure NOBr at a pressure of 3.8 atm and 300 K.
At equilibrium, the partial pressure of NOBr was 2.0 atm. Determine the value of Kp
for the reaction.
A) 0.81 B) 1.4 C) 0.73 D) 1.6 E) 0.90
24. Consider the decomposition of hydrazine as shown below.
N2H4 (g)  2H2 (g) + N2 (g)
At a certain temperature, Kp = 2.5 × 103 When pure hydrazine is placed in an
otherwise empty vessel at this temperature, equilibrium is reached after 30.0% of the
hydrazine has decomposed. Calculate the partial pressure of hydrogen gas at
equilibrium.
A) 54 atm B) 76 atm C) 127 atm D) 5776 atm E) none of these
25. Consider the following equilibrium: H2 (g) + I2 (s)  2HI (g)
∆H = +68.0 kJ/mol
Which of the following statements about the equilibrium is false?
A) If the system is heated, the right side is favored.
B) This is a heterogeneous equilibrium.
C) If the pressure on the system is increased by changing the volume, the left side is
favored.
D) Adding more H2 (g) increases the equilibrium constant.
E) Removing HI as it forms forces the equilibrium to the right.
26. The volume of a balloon is 3.78 L at 22.8°C. The balloon is heated to 42.4°C.
Calculate the new volume of the balloon.
A) 7.03 L B) 4.03 L C) 2.03 L
D) 3.55 L
E) 3.78 L
27. The volume of a helium balloon is 1.85 L at 24.0°C and 1.00 atm at sea level. The
balloon is released and floats upward. At a certain altitude, the balloon has a volume
of 2.14 L and the temperature is 15.2°C. What is the atmospheric pressure at this
altitude?
A) 0.538 atm B) 0.839 atm C) 0.891 atm D) 1.36 atm E) none of these
28. A 8.80 g piece of solid CO2 (dry ice) is allowed to sublime in a balloon. The final
volume of the balloon is 1.30 L at 310. K. What is the pressure of the gas?
A) 3.91 atm B) 0.256 atm C) 6.88 × 10-5 atm D) 1.72 × 102 atm E) 47.7 atm
29. Consider the following reaction, if 0.16 moles of O2 (g) and 0.20 mol of C are
allowed to completely
react in a 3.5 L container at 30 ºC, what is the final total pressure?
2C (s) + O2 (g) → 2 CO (g)
A) 1.11 atm B) 1.44 atm C) 1.85 atm D) 0.718 atm E) none of the
30. A gaseous mixture containing 1.5 mol Ar and 3.5 mol CO2 has a total pressure of
7.0 atm. What is the partial pressure of CO2?
A) 1.8 atm B) 2.1 atm C) 3.5 atm D) 4.9 atm E) 2.4 atm
31. Three 1.00 L flasks at 25°C and 725 torr contain the gases CH4 (flask A), CO2
(flask B), and C2H6 (flask C).
In which single flask do the molecules have the greatest mass, the greatest average
velocity, and the highest kinetic energy?
A) flask A B) flask B C) flask C D) all E) none
32. Under which of the following conditions does a gas behave most ideally?
A) STP
B) P = 1.0 atm, T = 100.0°C
C) P = 0.50 atm, T = 100.0°C
D) P = 0.50 atm, T = 0.0°C
E) P = 2.0 atm, T = -100.0°C
33. What volume of 0.450 M barium nitrate solution is needed to prepare 261.0 mL of
a solution that is 0.272 M in nitrate?
A) 158 mL B) 78.9 mL C) 316 mL D) 52.6 E) 432 mL
34. Reacting 47.4 mL of 0.320 M AgNO3 with 48.0 mL of 0.300 M K2CrO4 results in
what mass of solid formed?
A) 4.78 g B) 2.52 g C) 3.40 g D) 3.22 g E) 1.46 g
35. In the reaction Mg (s) + Pb(NO3)2 (aq) → Mg(NO3)2
agent.
A) Mg B) Pb(NO3)2 C) Mg(NO3)2 D) Pb E) O3
(aq)
+ Pb
(s),
identify the oxidizing
36. The following reaction occurs in aqueous acid solution:
NO3- + I-  IO3- + NO2
What is the coefficient for NO3- when balanced?
A) 2 B) 3 C) 4 D) 5 E) 6
37. TNT consists of carbon, nitrogen, oxygen, and hydrogen. It is 37.02% carbon by
mass, 18.49% nitrogen by mass, and 42.27% oxygen by mass. The molar mass of TNT
is between 210 g/mol and 245 g/mol. What is the molecular formula for TNT?
A) C7H5N3O6 B) C4H7N6O6 C) C8H12N3O4 D) C6H4N3O6 E) none of these
Answers 1. C 2. C 3. A 4. C 5. E 6. E 7. C 8. D 9. E 10. B 11. D 12. B 13. D 14. C 15.
C 16. B 17. E 18. D 19. A 20. A 21. C 22. B 23. C 24. B 25. D 26. B 27. B 28. A 29. C
30. D 31. E 32. C 33. B 34. B 35. B 36. E 37. A