Chem 1412 Exam The substance HOBr is considered

Transcription

1 Chem 1412 Exam 3 Student: 1. The substance HOBr is considered A.a weak Arrhenius acid. B.a weak Arrhenius base. C.a strong Arrhenius acid. D.a strong Arrhenius base. E.a neutral compound. 2. Which one of the following is a strong acid? A.H 2 CO 3 B.H 2 SO 3 C.H 2 SO 4 D.H 3 PO 4 E.CH 3 COOH 3. Which of the following pairs has the stronger acid listed first? A.HBr, HI B.HClO 2, HClO 3 C.H 2 SeO 4, H 2 SeO 3 D.HNO 2, HNO 3 E.HF, HCl 1

2 4. Which of the following liquids contains the strongest acid? 0.1 M HA, ph = M HD, ph = M HE, ph = M HJ, ph = pure water A.HE B.HA C.HJ D.HD E.pure water 5. What is the ph of a M HClO 4 solution? A B C D What is the ph of a M KOH solution? A.2.46 B.5.65 C.8.35 D What is the poh of a M KOH solution? A.2.07 B.4.77 C.9.23 D

3 8. What is the [OH - ] for a solution at 25 C that has ph = 4.29? A M B.5.l 10-5 M C M D M E.9.71 M 9. Select the pair of substances which is not a conjugate acid-base pair. A.H 3 O +, H 2 O B.HNO 2, NO 2 - C.H 2 SO 4, HSO 4 - D.H 2 S, S 2- E.NH 3, NH The acid dissociation constant K a equals for HSO 4 - and is for NH4 +. Which statement about the following equilibrium is correct? HSO 4 - (aq) + NH3 (aq) SO 4 2- (aq) + NH4 + (aq) A.The reactants will be favored because ammonia is a stronger base than the sulfate anion. B.The products will be favored because the hydrogen sulfate ion is a stronger acid than the ammonium ion. C.Neither reactants or products will be favored because all of the species are weak acids or bases. D.The initial concentrations of the hydrogen sulfate ion and ammonia must be known before any prediction can be made. E.This reaction is impossible to predict, since the strong acid and the weak base appear on the same side of the equation. 11. Butyric acid is responsible for the odor in rancid butter. A solution of 0.25 M butyric acid has a ph of What is the K a for the acid? A.0.36 B C D

4 12. Formic acid, which is a component of insect venom, has a K a = What is the [H 3 O + ] in a solution that is initially 0.10 M formic acid, HCOOH? A M B M C M D M E M 13. A 1.25 M solution of the weak acid HA is 9.2% dissociated. What is the ph of the solution? A.0.64 B.0.94 C.1.13 D What is the ph of a M triethylamine, (C 2 H 5 ) 3 N, solution? K b for triethylamine is A B.8.68 C.5.32 D.2.31 E.< What is the value of K b for the cyanide anion, CN -? K a (HCN) = A B C D E

5 16. What is the ph of a M triethanolammonium chloride, (HOC 2 H 2 ) 3 NHCl, solution? K b, ((HOC 2 H 2 ) 3 N) = A.2.75 B.4.89 C.9.11 D A solution is prepared by adding 0.10 mol of sodium fluoride, NaF, to 1.00 L of water. Which statement about the solution is correct? A.The solution is basic. B.The solution is neutral. C.The solution is acidic. D.The concentrations of fluoride ions and sodium ions will be identical. E.The concentration of fluoride ions will be greater than the concentration of sodium ions. 18. A solution is prepared by adding 0.10 mol of iron(iii) nitrate, Fe(NO 3 ) 3, to 1.00 L of water. Which statement about the solution is correct? A.The solution is basic. B.The solution is neutral. C.The solution is acidic. D.The value of K a for the species in solution must be known before a prediction can be made. E.The value of K b for the species in solution must be known before a prediction can be made. 19. An aqueous solution is prepared by dissolving the salt formed by the neutralization of a weak acid by a weak base. Which statement about the solution is correct? A.The solution is strongly basic. B.The solution is weakly basic. C.The solution is neutral. D.The solution is acidic. E.The values for K a and K b for the species in solution must be known before a prediction can be made. 5

6 20. Which of the following is a Lewis base? A.BCl 3 B.Cu 2+ C.Cl - D.Mn 2+ E.NH Equal volumes of the following pairs of solutions are mixed. Which pair will produce a buffer solution? A.0.10 mol L -1 HCl and 0.05 mol L -1 NaOH B.0.10 mol L -1 HCl and 0.15 mol L -1 NH 3 C.0.10 mol L -1 HCl and 0.05 mol L -1 NH 3 D.0.10 mol L -1 HCl and 0.20 mol L -1 CH 3 COOH E.0.10 mol L -1 HCl and 0.20 mol L -1 NaCl 22. Citric acid has an acid dissociation constant of It would be most effective for preparation of a buffer with a ph of A.2 B.3 C.4 D.5 E What will be the effect of adding 0.5 ml of 0.1 M NaOH to 100 ml of an acetate buffer in which [ CH 3 COOH] = [CH 3 COO - ] = 0.5 M? A.The ph will increase slightly. B.The ph will increase significantly. C.The ph will decrease slightly. D.The ph will decrease significantly. E.Since it is a buffer solution, the ph will not be affected. 6

7 24. A buffer is prepared by adding 0.5 mol of solid sodium hydroxide to 1.0 L of 1.0 M acetic acid ( CH 3 COOH). What is the ph of the buffer? A.The ph will be pk a , where pk a is that of acetic acid. B.The ph will be greater than the pk a for acetic acid. C.The ph will be less than the value in answer a. D.The ph will be equal to the pk a for acetic acid. E.More information is needed to solve the problem. 25. What is the ph of a buffer that consists of 0.45 M CH 3 COOH and 0.35 M CH 3 COONa? K a = A.4.49 B.4.64 C.4.85 D.5.00 E What is the [H 3 O + ] in a solution that consists of 1.2 M HClO and 2.3 M NaClO? K a = A M B M C M D M 27. A formic acid buffer containing 0.50 M HCOOH and 0.50 M HCOONa has a ph of What will the ph be after mol of NaOH has been added to ml of the buffer? A.3.67 B.3.78 C.3.81 D.3.85 E

8 28. A buffer is prepared by adding 150 ml of 1.0 M NaOH to 250 ml of 1.0 M NaH 2 PO 4. How many moles of HCl must be added to this buffer solution to change the ph by 0.18 units? A mol HCl B mol HCl C mol HCl D.0.50 mol HCl E.1.0 mol HCl 29. When a strong acid is titrated with a weak base, the ph at the equivalence point A.is greater than 7.0. B.is equal to 7.0. C.is less than 7.0. D.is equal to the pk a of the acid. E.is equal to the pk b of the base. 30. The indicator propyl red has K a = What would be the approximate ph range over which it would change color? A B C D A 20.0-mL sample of 0.30 M HBr is titrated with 0.15 M NaOH. What is the ph of the solution after ml of NaOH have been added to the acid? A.2.95 B.3.13 C D E

9 32. A 25.0-mL sample of 0.10 M C 2 H 3 NH 2 (ethylamine) is titrated with 0.15 M HCl. What is the ph of the solution after 9.00 ml of acid have been added to the amine? K b = A B C D E

10 33. A diprotic acid H 2 A has K a1 = and K a2 = The corresponding base A 2- is titrated with aqueous HCl, both solutions being 0.1 mol L -1. Which one of the following diagrams best represents the titration curve which will be seen? A. B. C. D. E. 10

11 34. A change in ph will significantly affect the solubility of which, if any, of the following compounds? A.BaF 2 B.CuCl C.CuBr D.AgI E.None of the solubilities will be significantly affected. 35. Write the ion product expression for silver sulfide, Ag 2 S. A. B. C. D. E. 36. The solubility of silver chromate is g/1.0 L of solution. What is the K sp for Ag 2 CrO 4? A B C D E.< Calculate the solubility of strontium fluoride, SrF 2, in pure water. K sp = A M B M C M D.5.l 10-5 M E.< M 11

12 38. Which of the following substances has the greatest solubility in water? A.Ba(IO 3 ) 2, K sp = B.PbF 2, K sp = C.SrSO 4, K sp = D.CuCl, K sp = E.CdS, K sp = A lab technician adds mol of KOH to 1.00 L of M Ca(NO 3 ) 2. K sp = for Ca(OH) 2Ẇhich of the following statements is correct? A.Calcium hydroxide precipitates until the solution is saturated. B.The solution is unsaturated and no precipitate forms. C.The concentration of calcium ions is reduced by the addition of the hydroxide ions. D.One must know K sp for calcium nitrate to make meaningful predictions on this system. E.The presence of KOH will raise the solubility of Ca(NO 3 ) The lab technician Anna Lytic adds 2.20 mol KOH to 1.00 L of 0.5 M Al(NO 3 ) 3. What is the concentration of aluminum ions after the aluminum nitrate has reacted with the potassium hydroxide? K f = for Al(OH) 4 - A M B.9.l M C M D M E.7.l M 12

13 Chem 1412 Exam 3 Key 1. (p. 772) A 2. (p. 772) C 3. (p. 772) C 4. (p. Sec. 18.1, 18.2) B 5. (p. 776) C 6. (p. 776) D 7. (p. 776) A 8. (p. 776) C 9. (p. 779) D 10. (p. 780) B 11. (p. 783) D 12. (p. 784) A 13. (p. 785) B 14. (p. 790) A 15. (p. 792) B 16. (p. 792) B 17. (p. 797) A 18. (p. 795) C 19. (p. 798) E 20. (p. 801) C 21. (p. 816) B 22. (p. 822) B 23. (p. 818) A 1

14 24. (p. 823) D 25. (p. 820) B 26. (p. 820) B 27. (p. 818) E 28. (p. 823) A 29. (p. 830) C 30. (p. 824) B 31. (p. 825) C 32. (p. 830) B 33. (p. 831) B 34. (p. 839) A 35. (p. 833) E 36. (p. 835) C 37. (p. 836) C 38. (p. 837) B 39. (p. 841) B 40. (p. 841) C 2

15 Chem 1412 Exam 3 Summary Category # of Questions Difficulty: E 9 Difficulty: H 10 Difficulty: M 21 Silberberg Acid Silberberg Ionic