CHEM 102: Sample Test 5

Transcription

1 CHEM 102: Sample Test 5 CHAPTER When H 2 SO 4 is dissolved in water, which species would be found in the water at equilibrium in measurable amounts? a. H 2 SO 4 b. H 3 SO + 4 c. HSO 4 d. SO 2 4 e. OH 2. Which of the following is the net ionic equation for the reaction that occurs during the titration of nitrous acid with potassium hydroxide? a) HNO 2 + K + + OH KNO 2 + H 2 O b) HNO 2 + H 2 O NO 2 + H 3 O + c) HNO 2 + KOH K + + NO 2 + H 2 O d) HNO 2 + OH NO 2 + H 2 O e) H + + OH H 2 O 3. What is the ph of a solution that is 0.2 M in acetic acid (K a = 1.8 x 10 5 ) and 0.2 M in sodium acetate? a) 4.7 b) 9.3 c) 7.0 d) 5.4 e) Given moles of NaC 2 H 3 O 2 and 0.05 moles of HC 2 H 3 O 2 dissolved in water, what is the ph? pk a for acetic acid is a b c d e. Cannot determine 5. If 50 ml of a 0.01 M HCl solution is titrated with a 0.01 M NaOH solution, what will be the initial ph and the ph at the endpoint. a. 2 and 3.5 b. 2 and 7 c and 7 d. 12 and 7 e. None of these 6. What is the ph of a 1.0 M aqueous solution of NaCl? a) 7.0 b) greater than 7.0 c) less than 7.0 d) there is not enough information given 7. A 50.00mL sample of M KOH is being titrated with M HNO 3. Calculate the ph of the solution after ml of HNO 3 is added. a) 6.50 b) 3.01 c) 2.71 d) 2.41 e) none of these 8. If the following substance is dissolved in pure water, will the solution be acidic, neutral, or basic? solid sodium carbonate: (Na 2 CO 3 ). a) acidic b) neutral c) basic 9. The HendersonHasselbach equation can be used to determine several factors. Which of the following can be determined? a. the ph for a solution of a strong acid and its conjugate base b. the ph for a strong base that has been partially titrated c. the mole ratio needed to make a buffer solution having a known ph d. the pk a of an equimolar mixture of an unknown weak acid and its conjugate base without knowing the ph e. the change in ph if some acid or base is added to a buffered solution 10. A 1 Liter buffered solution was prepared by dissolving 1.0 mole of NH 3 and 1.5 mole of NH 4 Cl in water. The ph of this solution would be: (K b = 1.8 x 10 5 ) a b. 9.0 c. 7.0 d. 4.0 e. none of the above 11. The salt that forms an alkaline (basic) aqueous solution is a. KNO 3. b. NH 4 Cl. c. NaC 2 H 3 O 2. d. NaCl.

2 12. A weak acid that has different colors for acid and its conjugate base can be used as a. an salt. b. an indicator. c. a buffer. d. a base. 13. Give the ph value of a solution 0.10 M in acetic acid (K a = 1.8 x 10 5 ) and 0.05 M in sodium acetate: a. 1.8 b. 2.4 c. 4.7 d. 4.4 e Methyl violet is an indicator used in acidbase titrations. Its acid form, HIn, is red, while its conjugate base from, In, is yellow. The color change occurs in the ph range In a solution of ph = 6.00 the color of the indicator will be a. red b. yellow c. orange d. colorless e. blue 15. In the titration of a weak acid HA with M NaOH, the stoichiometric point is known to occur at a ph value of approximately 11. Which of the following indicators would be best to use to mark the endpoint of this titration? a) an indicator with K a = b) an indicator with K a = 10 8 c) an indicator with K a = d) an indicator with K a = e) an indicator with K a = Calculate the ph of an aqueous solution of 2.0 M NH 4 Cl (K b for NH 3 =1.8 x 10 5 ). Choose your answer from the following ph ranges: a. ph = b. ph = c. ph = d. ph = e. ph = Assume that an indicator works BEST when the equivalent point of a titration comes in the middle of the indicator range. Which of the following indicators would be the best for a titration of ml of 0.10 M HC 2 H 3 O 2 (Ka=1.8 x 10 5 ) with ml 0.10 M NaOH? a. methyl violet b. methyl orange c. bromocresol green d. methyl red e. phenolphthalein Given a equimolar mixture of Benzoic acid and sodium benzoate what would be the ph of the solution? K a of HC 7 H 5 O 2 = 6.28 x 10 5 a b c d e. Cannot determine 19. A weak monoprotic acid (HA) is 1.41% dissociated in a 1.0 M solution. The K a for this acid is a. 4.0 x b. 5.6 x c. 2.0 x d. 9.9 x Buffer solution is one which a. contains the maximum amount of solute possible for a particular temperature. b. contains more than the expected amount of solute for a particular temperature and is therefore unstable. c. resists changes in ph upon addition of acid or base. d. contains an equal number of hydronium and hydroxide ions. e. changes color upon addition of strong base. 21. Which pair of compounds could be used to make a buffer solution? a. NaCl/HCl b. (NH 4 ) 2 SO 4 /H 2 SO 4 c. NaCH 3 COO/CH 3 COOH d. K 3 PO 4 /KH 2 PO 4 e. KOH/KBr 22. A salt which can be used to make a buffer with formic acid, HCOOH, is

3 a. NH 4 COOH b. KCOOH c. NaCl d. Na 2 CO 3 e. (NH 4 ) 3 PO Which two of the following compounds in aqueous solution would make an effective buffer solution? HNO 3 KNO 3 CH 3 COOH NH 4 NO 3 NH 3 a. HNO 3 & NH 4 NO 3 b. HNO 3 & KNO 3 c. CH 3 COOH & NH 3 d. NH 3 & NH 4 NO 3 e. CH 3 COOH & HNO Which combination of solutions is the best choice for making a buffer solution? a. equal volumes of 0.1 M formic acid and 0.1 M sodium formate b. equal volumes of 0.05 M hydrochloric acid and ammonium chloride c. equal volumes of 0.1 M sulfuric acid and M sodium sulfate d. equal volumes of 1 M acetic acid and M sodium acetate e. equal volumes of 0.5 M nitric acid and 0.5 M sodium hydroxide 25. Calculate the ph of a solution which is 0.05 M in lactic acid and 0.04 M in sodium lactate. The Ka for lactic acid is a b c d e Calculate the ph of a solution that contains 0.45 M benzoic acid and 0.40 M sodium benzoate. The K a for benzoic acid is a b c d e Which formula represents the HendersonHasselbach equation for the generic acid HA? a. pk a = ph + log b. ph = pk a log c. log = ph d. e. pk a ph = pk a + ph = pk a + log 28. Which pair of reagents is the best choice to make a buffer of ph = 4.50? a. HF/F Ka = b. CH 3 COOH/CH 3 COO Ka = c. H 2 PO 2 4 /HPO 4 Ka = d. NH + 4 /NH 3 Ka = e. HPO /PO 4 Ka =

4 29.Consider a buffer solution made up of H 2 PO 4 and HPO 2 4, which has a Ka of What ratio of HPO 2 4 to H 2 PO 4 will give a ph of 7.35? a to 1 b to 1 c. 1 to 1 d to 1 e. More information is needed to answer this question. 30. One liter of a buffer is prepared using equimolar amounts of ascorbic acid and sodium ascorbate, producing a solution with ph = 4.10 After addition of 10 ml of 1 M NaOH, the most likely value of the ph is a b c d e Calculate the ph of a buffer that is 0.14 M NH 3 and 0.10 M NH 4 NO 3. The Kb for ammonia is a b c d e Which is the smallest amount of solid NaOH shown that will exceed the buffer capacity of a 500. ml solution that is 0.40 M in acetic acid and 0.15 M in sodium acetate. The Ka for acetic acid is a g b g c g d g e g 33. Which statement about the titration of 0.10 M HNO 3 with 0.10 M KOH is not correct? a. The ph at the equivalence point is b. The initial ph is c. At the equivalence point the ph decreases sharply. d. At the equivalence point the volume of base added will be equal to the original volume of acid. e. The net ionic equation is H 3 O + + OH 2H 2 O. 34. Calculate the ph of a titration mixture when ml of M NaOH has been added to a ml sample of M HNO 3. a b c d e Calculate the volume of M NaOH needed to neutralize a ml sample of M HNO 3. a ml b ml c ml d ml e ml 36. Calculate the ph of a mixture of 51.0 ml of M NaOH and ml of M HNO 3. a b c d e. 2.19

5 37. Calculate the ph of a titration mixture when ml of M NaOH has been added to a ml sample of M CH 3 COOH. Ka = a b c d e Calculate the ph of a titration mixture at the midpoint of the titration of a ml sample of M CH 3 COOH with M NaOH. Ka = a b c d e Calculate the ph of a titration mixture at the equivalence point of the titration of a ml sample of M CH 3 COOH with M NaOH. Ka = a b c d e Calculate the ph of a titration mixture in which a ml sample of M CH 3 COOH has reacted with ml of M NaOH. Ka = a b c d e Which combination of acid and base would give the titration curve shown? a. NaOH and HCl b. KOH and H 3 PO 4 c. NH 4 OH and CH 3 COOH d. NaOH and H 2 SO 4 e. NH 4 OH and H 3 PO Acid "rain" is defined as any precipitation with a ph value less than. a. 1.0 b. 4.2 c. 5.6 d. 7.0 e Which list contains only compounds that directly contribute to acid rain? a. CaO, H 2 Se, Kr b. CO 2, SiO 2, GeO 2 c. Fe 2 S 3, CaCO 3, Na 2 CO 3 d. H 2 O, NH 3, CH 4 e. CO 2, NO 2, SO 2

6 44. Write the Ksp expression for silver phosphate, Ag 3 PO 4. a. [Ag + ] 3 [PO 3 4 ] b. [Ag ] [PO 4 ] [Ag 3PO4 ] c. 3x[Ag + ][PO 3 4 ] d. 3x[Ag + ] 3 + [PO 3 4 ] e. [H + ][OH ] 45. Calculate the molar solubility of silver chloride, AgCl. The Ksp = for silver chloride. a b c d e Calculate the molar solubility of silver chloride, AgCl, in a solution in which [Cl ] = M. Ksp = for silver chloride. a b c d e In which solution would calcium phosphate have the greatest solubility? a. 0.1 M phosphoric acid b. 0.1 M sodium phosphate c. saturated calcium hydroxide d. 0.1 M calcium nitrate e. distilled water 48. Which of the factors affecting solubility explains the observation that silver phosphate is more soluble in water than in Na 3 PO 4? a. The solubility of most salts increases as temperature increases. b. The solubility of many salts is affected by the ph of the solution. c. A common ion displaces the solubility equilibrium toward the undissolved solute. d. The formation of complex ions displaces the solubility equilibrium toward the aqueous ions. e. Some insoluble compounds are amphoteric. 49. Which of the factors affecting solubility explains the observation that the solubility of silver chloride is increased by the addition of NH 3 to the mixture? a. The solubility of most salts increases as temperature increases. b. The solubility of many salts is affected by the ph of the solution. c. A common ion displaces the solubility equilibrium toward the undissolved solute. d. The formation of complex ions displaces the solubility equilibrium toward the aqueous ions. e. Some insoluble compounds are amphoteric. 50. Which group contains only solutes that would decrease the solubility of barium sulfate? a. Ba(OH) 2, NaOH, NH 4 OH b. HNO 3, H 2 SO 4, HCH 3 COO c. Na 2 SO 4, NaOH, NaCH 3 COO d. Ba(NO 3 ) 2, Na 2 SO 4, H 2 SO 4 e. SO 2, CO 2, NH Which mixture would dissolve the largest amount of barium sulfate? a. 0.1 M HCl b. 0.1 M Ba(NO 3 ) 2 c. 0.1 M Mg(OH) 2 d. 0.1 M Na 2 SO 4 e. 0.1 M Al 2 (SO 4 ) Which mixture would dissolve the smallest amount of barium sulfate? a. 0.1 M HCl b. 0.1 M Ba(NO 3 ) 2

7 c. 0.1 M Mg(OH) 2 d. 0.1 M Na 2 SO 4 e. 0.1 M Al 2 (SO 4 ) Which of the following species would increase the solubility of CuI? a. NH 3 b. SO 4 2 c. OH d. S 2 O 3 2 e. CN 54. Will a precipitate form when 10.0 ml of 0.5 M NaCl is added to 10.0 ml of 0.05 M AgNO 3? The Ksp for AgCl is a. Yes because Q = K b. Yes because Q > K c. Yes because Q < K d. No because Q < K e. More information is needed to answer this question. 55. Calculate the volume of 0.10 M NaCl that must be added to 10.0 ml of 0.05 M AgNO 3 to begin forming a precipitate. The Ksp for AgCl is Dilution effects can be neglected; 1 ml = 20 drops. a. less than one drop b. 1.0 ml c. 2.5 ml d. 5.0 ml e ml Answers to Sample Test 4 Questions 1. c. HSO 4 2. d) HNO 2 + OH NO 2 + H 2 O 3. a) c) b) 2 and 7 6. a c c. basic 9. d. the pk a of an equimolar mixture of an unknown weak acid and its conjugate base without knowing the ph 10. b c. NaC 2 H 3 O b. an indicator. 13. c b. yellow 15. b. an indicator with K a = b. ph = d. methyl red a c. 2.0 x c. resists changes in ph upon addition of acid or base. 21. c. NaCH 3 COO/CH 3 COOH 22. b. KCOOH 23. d. NH 3 & NH 4 NO a. equal volumes of 0.1 M formic acid and 0.1 M sodium formate 25. c d e. ph = pk a + log

8 28. b. CH 3 COOH/CH 3 COO Ka = a to c e e g 33. c. At the equivalence point the ph decreases sharply. 34. e b ml 36. a c b d b b. KOH and H 3 PO c e. CO 2, NO 2, SO a. [Ag + ] 3 [PO 4 3 ] 45. c c e. distilled water 48. c. A common ion displaces the solubility equilibrium toward the undissolved solute. 49. d. The formation of complex ions displaces the solubility equilibrium toward the aqueous ions. 50. d. Ba(NO 3 ) 2, Na 2 SO 4, H 2 SO a. 0.1 M HCl 52. e. 0.1 M Al 2 (SO 4 ) a. NH b. Yes because Q > K 55. a. less than one drop