Dougherty Valley High School AP Chemistry Chapters 14 and 15 Test - Acid-Base Equilibria

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1 Dougherty Valley High School AP Chemistry Chapters 14 and 15 Test - Acid-Base Equilibria This is a PRACTICE TEST. Complete ALL questions. Answers will be provided so that you may check your work. I strongly suggest that you complete ALL of these problems. 1. For the equilibrium that exists in an aqueous solution of nitrous acid (HNO 2, a weak acid), the equilibrium constant expression is: A) [ H ][ NO K = 2] [ HNO2 ] B) 2 [ H ][ N][ O] K = [ HNO2 ] C) K = [H + ][NO 2 ] D) 2 [ H ] [ NO K = 2] [ HNO2 ] 2. What is the equilibrium constant for the following reaction? N 3 + H 3 O + HN 3 + H 2 O The K a value for HN 3 = 1.9 x A) 5.3 x B) 1.9 x 10 9 C) 1.9 x 10 5 D) 5.3 x 10 4 E) 1.9 x The equilibrium constants (K a ) for HCN and HF in H 2 O at 25 C are 6.2 x and 7.2 x 10 4, respectively. The relative order of base strengths is: A) F > H 2 O > CN B) H 2 O > F > CN C) CN > F > H 2 O D) F > CN > H 2 O 4. Calculate the [H + ] in a solution that has a ph of A) 2.9 M B) 11.1 M C) 1.1 x 10 3 M D) 8.9 x M

2 5. Solid calcium hydroxide is dissolved in water until the ph of the solution is The hydroxide ion concentration [OH - ] of the solution is: A) 5.1 x M B) 3.9 x 10 4 M C) 1.9 x 10 4 M D) 9.7 x 10 5 M 6. The pk a of HOCl is 7.5. Calculate the ph of a 0.50 M solution of HOCl. A) 7.5 B) 6.5 C) 3.9 D) 10.1 E) Calculate the poh of a 0.20 M solution of Ba(OH) 2. A) 0.70 B) 0.40 C) D) Determine the ph of a M solution of H 2 SO 4. The dissociation occurs in two steps. Ka 1 is extremely large; Ka 2 is 1.2 x A) B) 1.43 C) 1.92 D) 1.31 E) The [OH - ] in a 0.68 M pyridine (C 5 H 5 N; K b = 1.7 x 10-9 ) solution is A) 1.2 x 10 9 M B) 3.4 x 10 5 M C) 0.68 M D) 5.0 x 10 5 M 10. The conjugate acid and conjugate base of bicarbonate ion, HCO 3, are, respectively: A) H 3 O + and OH B) H 3 O + and CO 3 2 C) H 2 CO 3 and OH D) H 2 CO 3 and CO 3 2 E) CO 3 2 and OH

3 11. Which of the following species is present in the greatest concentration in a M H 2 SO 4 solution in H 2 O? A) H 3 O + B) HSO 4 C) H 2 SO 4 D) All species are in equilibrium and therefore have the same concentration. E) SO Which of the following is the correct order for increasing phs for HNO 3, KCl, NH 4 Cl, KOH, and NaC 2 H 3 O 2? (K a for HC 2 H 3 O 2 is 1.80 x 10 5, K a for NH 4 + is 5.56 x ). A) KCl, NH 4 Cl, HNO 3, KOH, NaC 2 H 3 O 2 B) HNO 3, KCl, NH 4 Cl, KOH, NaC 2 H 3 O 2 C) NH 4 Cl, HNO 3, KCl, KOH, NaC 2 H 3 O 2 D) HNO 3, NH 4 Cl, KCl, NaC 2 H 3 O 2, KOH 13. If K a for HCN is 6.16 x 10 10, what is K b for CN -? Note: CN H2O HCN OH A) 6.16 x B) 6.16 x 10 4 C) 1.62 x 10 5 D) 1.23 x 10 9 K b [ HCN][ OH ] [ CN ] 14. The hydrogen halides (HF, HCl, HBr, and HI) are all polar molecules. The strength of the acid each forms in water is based on which of the following? A) the polarity of the molecule B) the size of the molecule C) the strength of the bond D) two of these 15. Calculate the [H + ] in a solution that is 0.10 M in NaF and 0.20 M in HF. (K a = 7.2 x 10-4 ) A) 7.2 x 10 4 M B) 2.0 M C) 1.4 x 10 3 M D) 0.20 M

4 16. For a solution equimolar in HCN and NaCN, which statement is false? A) This is an example of the common ion effect. B) The [H + ] is larger than it would be if only the HCN was in solution. C) The [H + ] is equal to the K a. D) Addition of more NaCN will shift the acid dissociation equilibrium of HCN to the left. E) Addition of NaOH will increase [CN ] and decrease [HCN]. 17. Calculate the ph of a solution made by mixing ml of M NH 3 with ml of M HCl. (K b for NH 3 = 1.8 x 10-5.) A) 9.48 B) 4.52 C) 9.03 D) A titration of ml of 1.00 M H 2 A was done with 1.12 M NaOH. For the diprotic acid H 2 A, Ka 1 = 2.5 x 10-5, Ka 2 = 3.1 x Calculate the ph after ml of 1.12 M NaOH have been added. A) 9.29 B) 8.61 C) 5.39 D) 9.41 E) The ph at the equivalence point of a titration of a weak acid with a strong base will be A) less than B) equal to C) greater than D) More data is needed to answer this question. Use the following to answer questions 20-23: The following questions refer to the following system: 3.5 x 10 2 ml of 3.2 M Pb(NO 3 ) 2 and 2.0 x 10 2 ml of M NaCl are added together. K sp for the lead chloride is 1.6 x Determine Q, or the ion product. A) 1.1 x 10 4 B) 1.5 x 10 2 C) 7.8 x 10 3 D) 8.1 x 10 4

5 21. Will precipitation occur? A) Yes B) No C) Maybe, it depends on the temperature. D) Maybe, it depends on the limiting reagent concentration. E) None of these. 22. What is the limiting reagent in the formation of the lead chloride? A) Pb 2+ B) Cl C) (NO 3 ) D) PbCl 2 E) Pb(NO 3 ) Determine the equilibrium concentration of the chloride ion. A) 3.9 x 10 4 B) 8.0 x 10 6 C) 2.8 x 10 3 D) 6.1 x How many moles of HCl(g) must be added to 1.0 L of 1.6 M NaOH to achieve a ph of 0.00? (Neglect any volume change.) A) 0.6 moles B) 3.6 moles C) 2.6 moles D) 4.6 moles Use the following to answer questions 25-26: Consider a solution made by mixing ml of 4.0 M NH 3 and ml of 0.40 M AgNO 3. Ag + reacts with NH 3 to form AgNH 3 + and Ag(NH 3 ) 2 + : Ag + + NH The concentration of Ag(NH 3 ) 2 + at equilibrium is: A) 2.0 M B) 0.40 M C) 0.20 M D) 1.0 x 10 3 M

6 26. The concentration of Ag + at equilibrium is: A) 2.0 M B) 1.2 x 10 8 M C) 4.5 x 10 9 M D) 1.6 M 27. The K f for the complex ion Ag(NH 3 ) 2 + is 1.7 x The K sp for AgCl is 1.6 x Calculate the molar solubility of AgCl in 1.0 M NH 3. A) 5.2 x 10 2 B) 4.7 x 10 2 C) 2.9 x 10 3 D) 1.3 x 10 5 E) 1.7 x Find the solubility (in mol/l) of lead(ii) chloride (PbCl 2 ) at 25 o C. K sp = 1.56 x A) 1.57 x 10 2 B) 2.50 x 10 2 C) 5.93 x D) 1.97 x 10 3 E) 1.98 x It is observed that 7.50 mmol of BaF 2 will dissolve in 1.0 L of water. Use these data to calculate the value of K sp for barium fluoride. A) 1.1 x 10 4 B) 4.2 x 10 7 C) 1.7 x 10 6 D) 2.3 x 10 4 E) 5.6 x The K sp for PbF 2 is 4.0 x If a M NaF solution is saturated with PbF 2, what is the [Pb 2+ ] in solution? A) 5.6 x 10 7 M B) 2.0 x M C) 1.1 x 10 4 M D) 7.9 x 10 6 M E) 2.8 x 10 9 M