Chapter Test B. Chapter: Chemical Equilibrium. following equilibrium system? 2CO(g) O 2 (g) ^ 2CO 2 (g)

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1 Assessment Chapter Test B Chapter: Chemical Equilibrium PART I In the space provided, write the letter of the term or phrase that best completes each statement or best answers each question. 1. What is the effect on concentration if more CO(g) is added to the following equilibrium system? 2CO(g) O 2 (g) ^ 2CO 2 (g) a. [CO 2 ] increases and [O 2 ] decreases. b. Both [CO 2 ] and [O 2 ] increase. c. Both [CO 2 ] and [O 2 ] decrease. d. Both [CO 2 ] and [O 2 ] remain the same. 2. Consider the following equation for the ionization of acetic acid: CH 3 COOH(aq) H 2 O(l) ^ H 3 O (aq) CH 3 COO (aq) What is the equation for the acid ionization constant, K a, for this system? a. [H 3 O ][CH 3 COO ] b. c. d. [H 3 O ][CH 3 COO ] [CH 3 COOH] [H 3 O ][CH 3 COO ] [CH 3 COOH][H 2 O] [CH 3 COOH] [H 3 O ][CH 3 COO ] 3. Adding the salt of a weak base to a solution of the weak base a. lowers the concentration of the nonionized base and of OH. b. lowers the concentration of the nonionized base and raises the concentration of OH. c. raises the concentration of the nonionized base and of OH. d. raises the concentration of the nonionized base and lowers the concentration of OH. 4. A very high value for K indicates that a. reactants are favored. b. products are favored. c. equilibrium is reached slowly. d. equilibrium has been reached. Modern Chemistry 169 Chapter Test

2 5. How do K a values for weak and strong acids compare? a. K a (weak) K a (strong). b. K a (weak) K a (strong). c. K a (weak) K a (strong). d. K a is not defined for weak acids. 6. A reversible reaction is one in which a. only the forward reaction takes place. b. only the reverse reaction takes place. c. the products can react to reform the reactants. d. None of the above 7. If the ion product for two ions whose solutions have just been mixed is greater than the value of K sp, a. precipitation occurs. b. decomposition occurs. c. the solution is unsaturated. d. equilibrium cannot be achieved. PART II Write the correct term (or terms) in the space provided. 8. Salts of a weak acid and a strong base produce solutions that are 9. The equation for the self-ionization of water is. 10. Hydrolysis is a reaction between water and. 11. Equilibrium is a state. 12. The equilibrium expression for the reaction AgCl(s) ^ Ag (aq) Cl (aq) is 13. The is the phenomenon in which the addition of a charged particle common to two solutes decreases the solute concentration When small amounts of acids or bases are added to a solution of a weak acid and its salt, ph.. Modern Chemistry 170 Chapter Test

3 15. At equilibrium, the rate of the forward reaction is 16. In a chemical equilibrium expression, the shows concentration of reactants. the rate of the reverse reaction. 17. The equilibrium constant equation for the reaction NH 3 (g) H 2 O(l) ^ NH 4 (aq) OH (aq) is K b. 18. If the temperature of an equilibrium system is decreased, the reaction will be favored. 19. A change in pressure affects only equilibrium systems containing reactants in the. 20. If anions react with water, the process is called and the result is a more basic solution. 21. A solution that can resist changes in ph is called a(n) solution. 22. The equilibrium expression for the ionization of the weak acid HA is K a. PART III Write the answers to the following questions in the space provided. 23. Name three ways that chemical equilibrium can be disturbed. 24. Describe three situations in which ionic reactions go to completion. Modern Chemistry 171 Chapter Test

4 In the space provided, predict the effect that decreasing pressure would have on each of the following reaction systems at equilibrium. 25. H 2 (g) Cl 2 (g) ^ 2HCl(g) 26. 3O 2 (g) ^ 2O 3 (g) 27. CaCO 3 (s) ^ CaO(s) CO 2 (g) In the space provided, identify the following salt solutions as acidic, basic, or neutral M NaCl M NH 4 NO M Ca(CH 3 COO) M NH 4 CH 3 COO M NH 4 Cl In the space provided, state whether each system would produce an effective buffer solution. 33. H 3 PO 4 and Na 3 PO HCl and NaCl 35. KOH and KCH 3 COO 36. NH 3 and NH 4 Cl PART IV Write the answers to the following problems on the line to the left, and show your work in the space provided. 37. At equilibrium a 1.0 L vessel contains 20.0 mol of H 2, 18.0 mol of CO 2, 12.0 mol of H 2 O, and 5.9 mol of CO at 427 C. Calculate K at this temperature for the reaction described by the equation CO 2 (g) H 2 (g) ^ CO(g) H 2 O(g). Modern Chemistry 172 Chapter Test

5 38. Use the reaction E F ^ 2G and the equilibrium concentrations 0.60 mol/l for E, 0.80 mol/l for F, and 1.30 mol/l for G to calculate the equilibrium constant. E, F, and G are all gases. 39. What is the concentration of H 3 O ions in a solution of an acid HY that ionizes to produce H 3 O and Y ions? K a is , and the final concentration of HY is mol/l. 40. Calculate the solubility product constant of barium carbonate, BaCO 3. The solubility of this compound is g/100. ml of water. The atomic masses are C, 12.01; O, 16.00; Ba, What is the solubility in mol/l of copper(i) sulfide, Cu 2 S? Its K sp value is Calculate the ion product for 100 ml of M Pb(NO 3 ) 2 mixed with 200 ml of M NaCl. K sp for PbCl 2 is Does precipitation occur? Modern Chemistry 173 Chapter Test

6 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 g Mg g Mg 10 3 mol Mg Average rate (mo l Mg) t mol Mg 25 s mol/s 34. two 18 Chemical Equilibrium, pp 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

7 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 mol/l mol/l ; no 19 Oxidation-Reduction Reactions, pp 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 water and oxygen 26. disproportionation 27. reduced reduction 30. reduction 31. oxidation for Ca; 4 for C; 2 for O 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 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