Assessment Chapter Test A Chapter: Chemical Equilibrium In the space provided, write the letter of the term or phrase that best completes each statement or best answers each question. 1. A 15.0 ml volume of 0.0100 M Pb(NO 3 ) 2 is added to 15.0 ml of 0.0100 M NaI. A precipitate is formed, and equilibrium is established. The K sp equilibrium expression for the dissolution of PbI 2 is a. [Pb 2 [I 2. b. [Pb[I 2. c. [Pb 2 [2I 2. d. 2[Pb 2 [I. 2. What is the ion product for the PbI 2 reaction in question 1? a. 1.00 10 8 b. 1.25 10 7 c. 1.00 10 6 d. 2.5 10 5 3. What is the equilibrium expression for the following equation? Fe(OH) 3 (aq) ^ Fe 3 (aq) 3OH (aq) a. [F e 3 [ OH [Fe(OH) 3 3 3 ) 3 b. [F e [OH [ Fe( OH [ Fe( OH) c. 3 [F 3 e [OH 3 [Fe(OH) 3 d. [F e 3 [ OH 4. In a bottle of unopened cola, the CO 2 gas dissolved in the liquid is in equilibrium with the CO 2 gas above the liquid. The dissolved gas reacts with water molecules in the cola to form carbonic acid, which also dissociates into carbon dioxide and water. Which chemical equation(s) best describe this equilibrium system? a. CO 2 (g) ^ CO 2 (l) b. CO 2 (g) ^ CO 2 (aq) and CO 2 (l) H 2 O(l) ^ H 2 CO 3 (aq) c. CO 2 (g) ^ CO 2 (aq) d. CO 2 (g) ^ CO 2 (aq) and CO 2 (aq) H 2 O(l) ^ H 2 CO 3 (aq) Modern Chemistry 164 Chapter Test
5. The Haber process, N 2 (g) 3H 2 (g) ^ 2NH 3 (g) 92 kj, is operated at temperatures of about 500 C because a. a higher temperature would favor the products. b. K is a maximum at 500 C. c. the forward reaction rate is too slow at lower temperatures. d. K is equal to 1 at 500 C. 6. Which of the following would not affect the aqueous equilibrium reaction represented by the equation below? HNO 2 (aq) ^ H (aq) NO 2 (aq) a. the addition of NaNO 3 (s) b. an increase in H concentration c. the addition of NaNO 2 (s) d. a decrease in NO 2 concentration 7. Consider the equilibrium system represented by the equation below. H 2 O(l) 2CrO 2 4 (aq) ^ Cr 2 O 2 7 (aq) 2OH (aq) yellow orange If the hydroxide ions were removed, how would the color change? a. to darker yellow b. to lighter orange c. to darker orange d. not at all 8. The Fe ion present in acid mine drainage is colorless and surrounded by water molecules. If phenanthroline (Phe) is added, the solution turns orange as a colored complex is formed according to the equation Fe 3 H 2 O Phe ^ Fe 3 Phe H 2 O. The color is commonly used as an indicator of the Fe ion concentration. What would an increase in color from light to dark orange indicate in this system? a. an applied stress that shifted the equilibrium to favor the reverse reaction b. an applied stress that shifted the equilibrium to favor the forward reaction c. an increase in the rate of the reverse reaction d. addition of water to the system 9. The solubility product constant expression includes a. a concentration of zero for undissolved salt. b. the concentrations of dissolved and undissolved salt. c. an exponent corresponding to the charge on each ion. d. the concentrations of dissociated ions. Modern Chemistry 165 Chapter Test
10. In a reaction that goes nearly to completion, a. the re-formation of reactants is much slower than the formation of the products. b. the rate of the reverse reaction is faster than the rate of the forward reaction. c. the re-formation of reactants is much faster than the rate of formation of the products. d. the forward reaction rate increases. 11. Which of the following K eq expressions is correct for the formation of ammonia, NH 3, from its elements, as represented by the equation 3H 2 N 2 ^ 2NH 3 92 kj? [NH3 a. [H 2 3 [ N2 b. [H 2 3 [ N 2 [NH3 2 [NH c. 3 [H 2 [N2 d. [H 2 [N 2 [NH3 2 12. When you calculate the K sp of calcium fluoride, CaF 2, if the concentration of the F ion is 4.2 10 4 M, then the concentration of the Ca 2 ion is a. 2.1 10 4 M. b. 8.4 10 4 M. c. 4.2 10 4 M. d. 3.7 10 11 M. 13. Which of the following salts is least soluble? a. Ag 2 CO 3 K sp 8.4 10 12 b. Ag 2 CrO 4 K sp 1.1 10 12 c. AgI K sp 1.5 10 16 d. AgBr K sp 5.4 10 13 14. Consider the reaction represented by the equation 2NO(g) O 2 (g) ^ 2NO 2 (g). If the volume of the reaction chamber is decreased, then the a. forward reaction will be favored. b. reverse reaction will be favored. c. initial pressure of NO 2 will decrease. d. initial pressure of O 2 will remain constant. Modern Chemistry 166 Chapter Test
15. Consider the reaction represented by the equation Ag 2 SO 4 (aq) ^ 2Ag (aq) SO 4 2 (aq). You can shift the equilibrium to favor the reverse reaction by adding a. CaCl 2. b. AgNO 3. c. Na 2 SO 4. d. Both (b) and (c) 16. A chemical reaction that is at equilibrium always has a. a high K eq value. b. a forward reaction rate that equals the reverse reaction rate. c. equal concentrations of reactants and products. d. Both (a) and (b) 17. Which of these is true about the chemical equation below? reactants e products a. The concentration of the products is greater than the concentration of the reactants. b. K eq of the forward reaction has a low value. c. The reaction favors the products. d. K eq is equal to 1. 18. In which of the following reactions, described by the equations below, will an increase in pressure have no effect on the equilibrium of the system? a. 2NO 2 (g) ^ N 2 O 4 (g) b. 2NOCl(g) ^ 2NO(g) Cl 2 (g) c. H 2 O(g) CO(g) ^ H 2 (g) CO 2 (g) d. N 2 (g) 3H 2 (g) ^ 2NH 3 (g) 19. The common-ion effect promotes a. dissolution. b. precipitation. c. boiling. d. ionization. 20. What is the acid ionization expression for the equation HA(aq) H 2 O(l) ^ H 3 O (aq) A (aq)? a. [ A [ H3O [ HA [H O 2 [A b. [HA [ H2O c. [A [H3O [ HA d. [A [H 3 O [HA[H 2 O Modern Chemistry 167 Chapter Test
21. The reaction represented by the equation BH (aq) H 2 O(l) ^ H 3 O (aq) B(aq) is an example of a(n) a. cation hydrolysis reaction. b. anion hydrolysis reaction. c. conjugated reaction. d. ph reaction. 22. What is the value of K w? a. 1 10 14 b. 1 10 14 c. 1 10 7 d. 14 10 14 23. An example of a good buffer solution is one that contains a. HCl and NaCl. b. HNO 2 and NaCl. c. HNO 2 and NaNO 2. d. CH 3 COOH and NaCl. 24. When H 3 O ions are added to an aqueous solution of acetic acid, a. the reaction forms more CH 3 COO. b. the reaction forms more water. c. the reaction forms more CH 3 COOH. d. nothing happens. 25. Which of the following is a conjugate acid-base pair in the reaction represented by the equation below? H 2 PO 4 H 2 O ^ H 3 PO 4 OH a. H 2 PO 4 and H 2 O b. H 2 PO 4 and OH c. H 2 PO 4 and H 3 PO 4 d. None of the above Modern Chemistry 168 Chapter Test
TEACHER RESOURCE PAGE 24. Homogeneous reactions involve reactants and products that exist in a single phase. Heterogeneous reactions involve reactants in two different phases. 25. The energy of the activated complex is greater than the energy of the reactants and greater than the energy of the products. 26. nature of reactants, surface area, temperature, concentration, presence of catalysts 27. In order for a reaction to occur, the molecules or atoms must collide with sufficient energy to overcome the activation energy barrier. The collision also must occur in the correct orientation, in most cases at a particular end of a molecule or atom. 28. The rate law is determined from the slowest step, called the rate-determining step because it has the slowest rate. 29. Activated complex 30. Energy Energy E a Reactants Course of reaction With catalyst Product Course of reaction Without catalyst The activation energy is lower with a catalyst than without the catalyst, but the net energy change is the same for both reactions. 31. R k[a n [B m. R is the reaction rate, k is the specific rate constant, [A and [B are the molar concentrations of the reactants, and n and m are the respective powers to which the concentrations are raised. 32. R k[a 2 1 molmg 33. 0.060 g Mg 2.469 2 4.3 g Mg 10 3 mol Mg Average rate (mo l Mg) t 2.469 10 3 mol Mg 25 s 9.9 10 5 mol/s 34. two 18 Chemical Equilibrium, pp. 164 173 TEST A 1. a 2. c 3. b 4. d 5. c 6. a 7. c 8. b 9. d 10. a 11. a 12. a 13. c 14. d 15. d 16. b 17. b 18. c 19. b 20. c 21. a 22. a 23. c 24. c 25. c TEST B 1. a 2. b 3. d 4. b 5. b 6. c 7. a 8. basic 9. 2H 2 O(l) H 3O (aq) OH (aq) 10. dissolved ions 11. dynamic 12. K [Ag [Cl 13. common-ion effect 14. remains nearly constant 15. equal to 16. denominator 17. K [NH 4 [OH [ N H3 18. exothermic 19. gas phase or gas state 20. anion hydrolysis 21. buffered 22. K a [H 3O [ A [HA Modern Chemistry 233 Answer Key
TEACHER RESOURCE PAGE 23. changes in concentration, changes in pressure, changes in temperature 24. If a product is precipitated as a solid; if a gaseous product forms and escapes; if a soluble product is only slightly ionized 25. none 26. reverse reaction is favored 27. forward reaction is favored 28. neutral 29. acidic 30. basic 31. neutral 32. acidic 33. effective buffer 34. ineffective buffer 35. ineffective buffer 36. effective buffer 37. 0.20 38. 3.5 39. 1.79 10 3 mol/l 40. 1.2 10 8 41. 5.3 10 17 mol/l 42. 6.0 10 11 ; no 19 Oxidation-Reduction Reactions, pp. 174 182 TEST A 1. d 2. b 3. d 4. a 5. b 6. c 7. a 8. d 9. c 10. d 11. d 12. c 13. d 14. b 15. c 16. a 17. c 18. b 19. a 20. d 21. d 22. c 23. c 24. b 25. b TEST B 1. b 2. a 3. b 4. c 5. d 6. d 7. b 8. b 9. b 10. d 11. b 12. d 13. b 14. b 15. b 16. b 17. d 18. b 19. d 20. d 21. d 22. c 23. a 24. 4 25. water and oxygen 26. disproportionation 27. reduced 28. 1 29. reduction 30. reduction 31. oxidation 32. 2 for Ca; 4 for C; 2 for O 33. 2 for Fe; 5 for N; 2 for O 34. redox 35. nonredox 36. redox 37. Zn(s) 3 Zn 2 2e 38. Cl 2 (g) 2e 3 2Cl (g) 39. Zn(s) Cl 2 (g) 3 ZnCl 2 (s) 40. K 2 Cr 2 O 7 14HCl 3 2KCl 2CrCl 3 7H 2 O 3Cl 2 20 Electrochemistry, pp. 183 192 TEST A 1. b 2. d 3. d 4. c 5. c 6. d 7. a 8. c 9. d 10. a 11. b 12. b 13. b 14. a 15. c 16. a 17. d 18. d 19. d 20. b 21. a 22. a 23. b 24. a 25. c TEST B 1. d 2. b 3. a 4. b 5. b 6. c 7. a 8. d 9. b 10. b 11. cathode 12. electrochemistry 13. electric energy 14. anode 15. voltaic cell Modern Chemistry 234 Answer Key