Florida Gulf Coast University Equilibrium and Acid Bases Chemistry Questions

Chapter 14: Acid-Base EquilibriaHomework
Answer the quesions on this hardcopy first, then enter your answer keys on Canvas to get credit. To enter the
keys, click “Assignments” on the left panel of the course homepage, and then select the corresponding chapter to
work on.
1. Rank the following acids in order of increasing acidity: H2O, H2S, H2Se, H2Te.
A. H2O, H2S, H2Se, H2Te.
B. H2Te, H2Se , H2S, H2O.
C. H2O, H2Te, H2Se, H2S.
2. When titrating a weak base with a strong acid, approximately where would the pH be
observed when reaching the equivalence point?
A. at the equivalence point, the pH is greater than 7
B. at the equivalence point, the pH is equal to 7
C. at the equivalence point, the pH is less than 7
3. When titrating a strong acid with a strong base, approximately where would the pH be
observed when reaching the equivalence point?
A. at the equivalence point, the pH is greater than 7
B. at the equivalence point, the pH is equal to 7
C. at the equivalence point, the pH is less than 7
4. Phenolphthalein can be used as an _____ in acid-base titrations.
A. equivalence point
B. end-point
C. indicator
5. Which of the following is a diprotic acid?
A. H3PO4
B. H2PO4C. HPO426. Which of the following is an amphiprotic substance?
A. H3PO4
B. PO43C. HPO427. Rank the following oxyanions in order of increasing basicity SO32- , SO42-.
A. SO32- < SO42B. SO42- < SO328. Rank the following oxoacids in order of increasing acidity: HClO2, HClO4, HClO, HClO3. A. HClO, HClO2, HClO3, HClO4 B. HClO4, HClO2, HClO, HClO3 Page 1 of 5 C. HClO4, HClO3, HClO2, HClO 9. If 3 mL of a 0.5 M HBr solution is added to 20 mL of a 0.5 M NaOH solution, the resulting solution would be _____. A. acidic B. basic C. neutral 10. A student titrates a 25 mL of an unknown concentration of HCl with 35 mL of a 0.890 M solution of KOH to reach the equivalence point. What is the pH of the HCl solution? A. -0.10 B. 0.10 C. 1.2 11. What is the pH of 0.014 M solution of hydroiodic acid? A. 1.4 B. 1.9 C. 0.85 12. What is the hydroxide ion concentration for a 3.65 M HNO3 solution? A. 10.35 M B. 3.65 M C. 2.74 x 10-15 M 13. Blood is considered a buffered solution. What is the pH range of blood? A. 7.35 - 7.45 B. 6.35 - 6.45 C. 8.35 - 8.45 14. Which acid has a lower pH? A. 1.0 M acetic acid B. 0.50 M acetic acid C. 0.25 M acetic acid 15. Which acid has a higher hydrogen ion concentration? A. 1.0 M HCl B. 0.050 M HNO3 C. 1.25 M HBr 16. What is the base in the following reaction: HCl (aq) + H2O (l)  Cl- (aq) + H3O+ (aq)? A. ClB. H3O+ C. H2O 17. What is the conjugate acid of HSO4-? A. H2SO4 B. SO42- Page 2 of 5 C. H2SO418. What is the pOH of a solution that has a pH of 2? A. 12 B. 7 C. 14 19. Which acid has the lowest hydroxide ion concentration? A. 0.010 M HCl B. 0.050 M HNO3 C. 0.015 M HBr 20. State which of the following species are amphiprotic: (a) H2O (b) H 2 PO 4  (c) S2– (d) CO 3 2  (e) HSO 4  A. (a), (b) and (c) B. (a), (b) and (e) C. (a), (c) and (e) 21. Identify and label the Brønsted-Lowry acid, its conjugate base, the Brønsted-Lowry base, and its conjugate acid in the following equation: NO2   H 2O   HNO2  OH  A: Brønsted-Lowry acid and its conjugate base: H2O and OH-, respectively; Brønsted-Lowry base and its conjugate acid: NO2- and HNO2, respectively. B: Brønsted-Lowry acid and its conjugate base: NO2- and HNO2 , respectively; Brønsted-Lowry base and its conjugate acid: H2O and OH-, respectively. C: Brønsted-Lowry acid and its conjugate base: NO2- and OH-, respectively; Brønsted-Lowry base and its conjugate acid: H2O and HNO2, respectively. 22. Identify and label the Brønsted-Lowry acid, its conjugate base, the Brønsted-Lowry base, and its conjugate acid in the following equation: [Fe(H 2O)5 (OH)]2  [Al(H 2O) 6 ]3   [Fe(H 2O) 6 ]3  [Al(H 2O)5 (OH)]2 A: Brønsted-Lowry acid and its conjugate base: [Al(H2O)6]3+ and [Fe(H2O)6]3+, respectively; Brønsted-Lowry base and its conjugate acid: [Fe(H2O)5(OH)]2+ and [Al(H2O)5(OH)]2+, respectively. B: Brønsted-Lowry acid and its conjugate base: [Fe(H2O)5(OH)]2+ and [Fe(H2O)6]3+, respectively; Page 3 of 5 Brønsted-Lowry base and its conjugate acid: [Al(H2O)6]3+ and [Al(H2O)5(OH)]2+, respectively. C: Brønsted-Lowry acid and its conjugate base: [Al(H2O)6]3+ and [Al(H2O)5(OH)]2+, respectively; Brønsted-Lowry base and its conjugate acid: [Fe(H2O)5(OH)]2+ and [Fe(H2O)6]3+, respectively. 23. The pH of a 0.10-M solution of caffeine is 11.70. Determine Kb for caffeine from these data: C8H10N4O2 (aq) + H2O (l)  C8H10N4O2H+ (aq) + OH- (aq) A. 2.6 x 10-4 B. 2.3 C. 0.00501 D. 0.095 24. Propionic acid, C2H5COOH (Ka = 1.34  10–5), is used in the manufacture of calcium propionate, a food preservative. What is the pH of a 0.698-M solution of C2H5CO2H? C2H5COOH (aq) + H2O (l)  H3O+ (aq) + C2H5COO - (aq) A. 3.058  10–3 B. 2.515 C. 0.698 25. Determine whether a solution of FeCl3 are acidic, basic, or neutral: A. acidic B. basic C. neutral 26. Determine whether a solution of KClO4 are acidic, basic, or neutral: A. acidic B. basic C. neutral 27. What is [OH–] in a solution of 1.25 M NH3 and 0.78 M NH4NO3? NH3 (aq) + H2O (l)  NH4 + (aq) + OH- (aq) Kb =1.8 x 10-5 – –3 A. [OH ] = 3.9  10 M B. [OH–] = 1.9  10–4 M C. [OH–] = 2.9  10–5 M 28. Explain why the pH does not change significantly when a small amount of an acid or a base is added to a solution that contains equal amounts of the base NH3 and a salt of its conjugate acid NH4Cl. A. Excess base is removed primarily by reacting with H2O; excess acid is removed by reacting with NH3 B. Excess base is removed primarily by reacting with NH4Cl; excess acid is removed by reacting with NH3 C. Excess base is removed primarily by reacting with NH3; excess acid is removed by reacting with NH4Cl Page 4 of 5 29. Which of the following titration curve represents a titration of a weak acid with a strong base. A. the one on the left B. the one on the right 30. Based on the tritration curve shown below, what’s the pKa of the acid being titrated? A. pKa=4.0 B. pKa=4.7 B. pKa=5 Page 5 of 5 Chapter 13: Fundamental Equilibrium Concepts Homework Answer the quesions on this hardcopy first, then enter your answer keys on Canvas to get credit. To enter the keys, click "Assignments" on the left panel of the course homepage, and then select the corresponding chapter to work on. 1. What does it mean to describe a reaction as “reversible”? A. The reaction can proceed in both the forward and reverse directions B. The reaction can proceed in the forward direction, not reverse direction. C. The reaction can not proceed in the forward direction, but can proceed in the reverse direction. 2. Consider the following equilibrium mixture in a closed system: H2O(g) + CO(g) ⇌ H2(g) + CO2(g). Explain what would happen to the equilibrium upon the addition of hydrogen gas? A. The addition of hydrogen gas would disrupt the equilibrium causing it to shift towards the left until new equilibrium is achieved. B. The addition of hydrogen gas would disrupt the equilibrium causing it to shift towards the right until new equilibrium is achieved. C. The addition of hydrogen gas would not disrupt the equilibrium, so nothing would happen. 3. Write the equilibrium expression for 2NO(g) + 2H2(g) ⇌ N2(g) + 2H2O(g). A. Kc = B. Kc = [NO]2 [H2 ]2 [H2 O]2 [𝑁2 ] [H2 O]2 [𝑁2 ] [NO]2 [H2 ]2 [𝑁 ] C. Kc = [NO]22[H 2] 2 4. The Kc for the formation of HI from iodine and hydrogen gas is 54. If the concentrations of HI, I2, and H2 are 5.338 M, 0.112 M, and 0.198 M respectively, which statement is correct? H2 +I2 ⇌ 2HI A. Q = 5.15 which is less than Kc, therefore the reaction needs to proceed towards the right to reach equilibrium B. Q = 15.2 which is less than Kc, therefore the reaction needs to proceed towards the right to reach equilibrium C. Q = 1284 which is more than Kc, therefore the reaction needs to proceed towards the left to reach equilibrium 5. Among the solubility rules: All chlorides are soluble except Hg2Cl2, AgCl, PbCl2, and CuCl.Write the expression for the equilibrium constant for the reaction represented by the equation Ag+ (aq) + Cl- (aq)  AgCl(s). Is Kc > 1, < 1, or ≈ 1? A. B. C. D. [Ag+ ][Cl− ] , Kc > 1
[𝐴𝑔𝐶𝑙]
1
, Kc >
[Ag+ ][Cl− ]
1
, Kc < [Ag+ ][Cl− ] [Ag + ][Cl− ], 1 1 Kc > 1
6. Among the solubility rules: All chlorides are soluble except Hg2Cl2, AgCl, PbCl2, and
CuCl.Write the expression for the equilibrium constant for the reaction represented by the
equation
PbCl2(s)  Pb2+ (aq) + 2Cl- (aq). Is Kc > 1, < 1, or ≈ 1? A. [𝑃𝑏 2+ ][Cl− ] 2 , Kc > 1
[𝑃𝑏𝐶𝑙2 ]
[𝑃𝑏 2+ ][Cl− ] 2
B.
, Kc > 1
1
C. [𝑃𝑏2+][Cl−] 2, Kc < 1 D. [𝑃𝑏 2+ ][Cl− ] 2 , Kc < 1 7. Write the mathematical expression for the reaction quotient, Qc, for the following reaction: CH4(g) + Cl2 (g) ⇌ CH3Cl (g) + HCl (g) A. 𝑄𝑐 = [𝐶𝐻3 𝐶𝑙][𝐻𝐶𝑙] [𝐶𝐻4 ][𝐶𝑙2 ] [𝐶𝐻4 ][𝐶𝑙2 ] B. 𝑄𝑐 = [𝐶𝐻 C. 𝑄𝑐 = 3 𝐶𝑙][𝐻𝐶𝑙] [𝐶𝐻3 𝐶𝑙][𝐻𝐶𝑙] [𝐶𝐻4 ] 8. Write the mathematical expression for the reaction quotient, Qc, for the following reaction: P4(s) + 5O2 (g) ⇌ P4O10 (s) [𝑃4 𝑂10 ] A. 𝑄𝑐 = [𝑃 ][𝑂 ] 4 2 [𝑃4 𝑂10 ] B. 𝑄𝑐 = [𝑃 4 ][𝑂2 ] 5 1 C. 𝑄𝑐 = [𝑂 2] 5 9. Write the mathematical expression for the reaction quotient, Qc, for the following reaction: CH4(g) + 2O2 (g) ⇌ CO2 (g) + 2H2O (l) A. 𝑄𝑐 = B. 𝑄𝑐 = C. 𝑄𝑐 = [𝐻2 𝑂]2 [𝐶𝑂2 ] [𝐶𝐻4 ][𝑂2 ]2 [𝐶𝑂2 ] [𝐶𝐻4 ][𝑂2 ]2 [𝐶𝑂2 ] [𝐶𝐻4 ][𝑂2 ] 10. Which of the systems described below are homogeneous equilibria? Which are heterogeneous equilibria? (1) CuSO45H2O(s) ⇌ CuSO4 (s) + 5H2O (g) (2) CH4(g) + 2O2 (g) ⇌ CO2 (g) + 2H2O (l) (3) CH4(g) + Cl2 (g) ⇌ CH3Cl (g) + HCl (g) (4) N2(g) + O2 (g) ⇌ 2NO (g) (5) P4(s) + 5O2 (g) ⇌ P4O10 (s) A. homogenous: (1), (2), and (5); heterogeneous: (3), (4) B. homogenous: (1), (2), and (3); heterogeneous: (4), (5) C. homogenous: (3), and (4); heterogeneous: (1), (2) and (5) 11. The initial concentrations or pressures of reactants and products are given for the following system. Calculate the reaction quotient and determine the direction in which each system will proceed to reach equilibrium. 2NH3 (g) ⇌ N2(g) + 3H2 (g), Kc =17; [NH3] = 0.50 M, [N2] = 0.15 M, [H2] = 0.12 M A. Qc= 1.0 X 10-3 , proceeds right B. Qc= 1.0 X 103 , proceeds left A. Qc= 1.0 X 10-2 , proceeds right 12. The initial concentrations or pressures of reactants and products are given for the following system. Calculate the reaction quotient and determine the direction in which each system will proceed to reach equilibrium. 2SO3 (g) ⇌ 2SO2(g) + 3O2 (g), KP=6.5; SO2 = 1.00 atm, O2 = 1.130 atm, SO3 = 0 atm A. Qc= infinitely large , proceeds right B. Qc= infinitely large , proceeds left C. Qc= 1.13, proceeds right 13. For which of the following reactions does Kc (calculated using concentrations) equal KP ? (1) MgSO47H2O(s) ⇌ MgSO4 (s) + 7H2O (g) (2) CH4(g) + 2O2 (g) ⇌ CO2 (g) + 2H2O (g) (3) CH4(g) + Br2 (l) ⇌ CH3Cl (g) + HCl (g) (4) N2(g) + O2 (g) ⇌ 2NO (g) (5) P4(s) + 5O2 (g) ⇌ P4O10 (s) A. (3) and (4) B. (1), (2), and (5) C. (2) and (4) 14. Convert the values of Kc to values of KP. KP = Kc(RT)Δn Cl2(g) + Br2 (g) ⇌ 2BrCl(g) Kc = 4.7 x10-2 at 25OC A. Δn = (2) – (1 + 1) = 0, KP = Kc(RT)0 = Kc = 4.7 × 10–2 B. Δn = (2) – (1) = 1, KP = Kc(RT)1 = 4.7 × 10–2 (0.08206  298.15) = 1.2 C. Δn = (1) – (1 + 1) = -1, KP = Kc(RT)-1 = 4.7 × 10–2 (0.08206  298.15) -1 = 1.9 × 10–3 15. Write the expression of the reaction quotient for the ionization of HOCN in water. H2O(l) + HOCN(aq) ⇌ H3O+ (aq) + OCN- (aq) A. 𝑄𝑐 = [𝐻3 𝑂 + ] [𝑂𝐶𝑁− ] [𝐻𝑂𝐶𝑁][𝐻2 𝑂] [𝐻3 𝑂 + ] [𝑂𝐶𝑁 − ] [𝐻𝑂𝐶𝑁] [𝐻2 𝑂] [𝐻𝑂𝐶𝑁] B. 𝑄𝑐 = C. 𝑄𝑐 = [𝐻 3𝑂 +] [𝑂𝐶𝑁 − ] 16. Changes in volume may or may not affect gas-phase systems at equilibrium. Explain how to
recognize the conditions under which changes in volume will affect gas-phase systems at
equilibrium
A. An effect arises only when the number of moles of gaseous reactants in the equation differs
from the number of moles of gaseous products.
B. As the volume of a gaseous system decreases, the gases become compressed, producing
greater molar concentrations. This change in concentration represents a stress on the system, and
the system will act to remove the stress, shifting the equilibrium to the side with the more
number of moles.
C. An effect arises only when the number of moles of gaseous reactants in the equation is the
same as the number of moles of gaseous productsA.
17. A necessary step in the manufacture of sulfuric acid is the formation of sulfur trioxide SO3, from
sulfur dioxide, SO2, and oxygen, O2 shown here.
SO2 (g) + O2 (g) ⇌ SO3 (g)
At high temperatures, the equilibrium amount (concentration or partial pressure) of SO3 is
lower than it would be at lower temperatures. Does the equilibrium constant for the reaction
increase, decrease, or remain about the same as the temperature increases? Is the reaction
endothermic or exothermic?
A. The equilibrium constant decreases as the temperature increase as less product is collected at
higher temperature. The reaction is exothermic.
B. The equilibrium constant decreases as the temperature increase as less product is collected at
higher temperature. The reaction is endothermic.
C. The equilibrium constant increases as the temperature increase. The reaction is exothermic.
18. Suggest ways in which the concentration of hydrazine, N2H4, could be increased in an
equilibrium described by the following equation:
N2(g) + 2H2 (g) ⇌ N2H4 (g)
∆H=95 kJ
A. Add N2;
B. Add H2;
C. Decrease the container volume
D. Heat the mixture
E. All of the above
19. Methanol can be prepared from carbon monoxide and hydrogen at high temperature and pressure
in the presence of a suitable catalyst.
2H2(g) + CO (g) ⇌ CH3 OH(g)
∆H=-90.2 kJ
What will happen to the concentrations of H2, CO, and CH3OH at equilibrium if CO is
removed?
A. [H2] decreases, [CO] decreases, [CH3OH] increases
B. [H2] increases, [CO] decreases, [CH3OH] increases
C. [H2] increases, [CO] decreases, [CH3OH] decreases
20. How will an increase in temperature affect each of the following equilibrium? How will a
decrease in the volume of the reaction vessel affect it?
N2(g) + O2 (g) ⇌ 2NO (g) , ∆H= 181 kJ
A. An increase in temperature will shift the equilibrium to the left; a decrease in the volume of
the reaction vessel will shift the equilibrium to the right.
B. An increase in temperature will shift the equilibrium to the right; a decrease in the volume of
the reaction vessel will shift the equilibrium to the right.
C. An increase in temperature will shift the equilibrium to the right; a decrease in the volume of
the reaction vessel will not affect the equilibrium.
21. Calculate the value of the equilibrium constant KP for the reaction 2NO (g) + Cl2 (g) ⇌ 2NOCl
(g) from these equilibrium pressures: NO, 0.050 atm; Cl2, 0.30 atm; NOCl, 1.2 atm.
A. 1.9 x 102
B. 1.9 x 103
C. 1.5 x 102
D. 1.5 x 103
22. A sample of ammonium chloride was heated in a closed container. NH4 Cl(s) ⇌ NH3(g) + HCl
(g) At equilibrium, the pressure of NH3(g) was found to be 1.75 atm. What is the value of the
equilibrium constant KP for the decomposition at this temperature
A. 0.1256
B. 3.06
C. 0.0306
D. 0.01256
23. A 0.72-mol sample of PCl5 is put into a 1.00-L vessel and heated. At equilibrium, the vessel
contains 0.40 mol of PCl3(g) and 0.40 mol of Cl2(g). Calculate the value of the equilibrium
constant for the decomposition of PCl5 to PCl3 and Cl2 at this temperature.
PCl5(g) ⇌ PCl3(g) + Cl2(g)
A. 0.5
B. 2.0
C. 1.0
D. 1.5
24. Assume that the change in concentration of N2O4 is small enough to be neglected in the
following problem. Calculate the equilibrium concentration of NO2 in 1.00 L of a solution
prepared from 0.129 mol of N2O4 with chloroform as the solvent.
N2O4 (g) ⇌ 2NO2 (g)
Kc = 1.07 x 10-5 in chloroform
A. [NO2] = 5.87  10–4M
B. [NO2] = 1.17  10–3 M
C. [NO2] = 0.128 M
25. Assume that the change in pressure of H2S is small enough to be neglected in the following
problem. Calculate the equilibrium pressures of S2 in an equilibrium mixture that results from the
decomposition of H2S with an initial pressure of 0.824 atm.
2H2S (g) ⇌ S2(g) + 2H2 (g) KP = 2.2 x 10-6
A. 0.810 atm
B. 0.014 atm
C. 0.0072 atm
26. What is the concentration of HClO after a mixture that contains [H2O] = 2.00 M and [Cl2O] =
2.00 M comes to equilibrium at 25 C?
H2O(g) + Cl2O(g) ⇌ 2HClO(g)
Kc = 0.0900
A. 0.153 M
B. 0.307 M
C. 0.522 M
27. Calculate the equilibrium constant at 25C for the following reaction from the value of ΔG
given.
O2 (g )  2F2 ( g ) 
 2OF2 ( g )
G  – 9.2 kJ
A. K = 21
B. K = 31
C. K = 41
28. Calculate the equilibrium constant at 25C for the following reaction from the value of ΔG
given.
I2 (s)  Br2 (l ) 
 2IBr(g )
G  7.3 kJ
A. K = 0.53
B. K = 0.053
C. K = 0.0053
29. Calculate ΔG for the following reaction from the equilibrium constant at the temperature given.
Cl2 (g )  Br2 ( g ) 
 2BrCl(g )
T  25 C
K P  4.7  102
A. ΔG° = -4.6 kJ;
B. ΔG° = -5.6 kJ
C. ΔG° = 7.6 kJ
30. Calculate ΔG for the following reaction from the equilibrium constant at the temperature given.
2SO2 (g) + O2 (g)  2SO3 (g)
T=500OC
KP =48.2
A. ΔG° =
B. ΔG° =
C. ΔG° =
D. ΔG° =
24.9 kJ;
-24.9 kJ
14.9 kJ
-14.9 kJ