CHM 1046 Test #4 April 24, 2001

Transcription

1 CHM 1046 Test #4 April 24, 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 2. The substance (CH 3 CH 2 ) 2 NH is considered a. a weak acid b. a weak base c. a strong acid d. a strong base 3. Which of the following acids has the lowest ph? 0.1 M HBO, pk a = M HA, pk a = M HMO, pk a = M HST, pk a = a. HA b. HST c. HMO d. HBO 4. Which of the following solutions contains the strongest acid? a. HE b. HA c. HJ d. HD 0.1 M HA, ph = M HD, ph = M HE, ph = M HJ, ph = What is the ph of a 0.20 M HCl solution? a b c d

2 6. What is the ph of a M KOH solution? a b c d What is the [OH - ] for a solution at 25 C that has [H 3 O + ] = M? a M b M c M d M 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 9. Select the pair of substances in which an acid is listed followed by its conjugate base. a. + NH 3, NH 4 b. HPO , H 2 PO 4 c. HCO - 2-3, CO 3 d. + CH 3 COOH, CH 3 COOH 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 A student adds 0.1 mol of oxalic acid and 0.1 mol of sodium dihydrogen phosphate to enough water to make 1.0 L of solution. The following equilibrium is established with the concentrations of the products greater than the concentrations of the reactants. Which of the statements about the equilibrium system is correct? H 2 C 2 O 4 (aq) + H 2 PO 4 - (aq) HC 2 O 4 - (aq) + H 3 PO 4 (aq) a. Oxalic acid is a weaker acid than phosphoric acid. b. The hydrogen oxalate anion, HC 2 O - 4, is a stronger base than the dihydrogen phosphate anion, H 2 PO - 4. c. Phosphoric acid is a weaker acid than oxalic acid. d. The dihydrogen phosphate anion, H 2 PO - 4, is a stronger acid than oxalic acid. 2

3 12. 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 b c d 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 14. What is the ph of a M triethylamine, (C 2 H 5 ) 3 N, solution? K b = a b c d What is the value of K b for the formate anion, HCOO -? K a (HCOOH) = a b c d

4 16. What is the ph of a M sodium benzoate solution? K b (C 7 H 5 O 2 - ) = a b c 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 values for K a and K b for the species in solution must be known before a prediction can be made. 18. A solution is prepared by adding 0.10 mol of sodium sulfide, Na 2 S, 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 values for K a and K b for the species in solution must be known before a prediction can be made. 19. 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 values for K a and K b for the species in solution must be known before a prediction can be made. 20. Which one of the following substances will give an aqueous solution of ph closest to 7? a. KNO 3 b. CO 2 c. NH 4 I d. NH 3 e. CH 3 NH 2 4

5 21. Which of the following aqueous mixtures would be a buffer system? a. HCl, NaCl b. HNO 3, NaNO 3 c. - H 3 PO 4, H 2 PO 4 d. H 2 SO 4, CH 3 COOH 22. Which of the following acids should be used to prepare a buffer with a ph of 4.5? a. HOC 6 H 4 OCOOH, K a = b. C 6 H 4 (COOH) 2, K a = c. CH 3 COOH, K a = d. C 5 H 5 O 5 COOH -2, K a = What is the ph for a buffer that consists of 0.45 M CH 3 COOH and 0.35 M CH 3 COONa? K a = a b c d When a strong acid is titrated with a strong 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. 25. When a weak acid is titrated with a strong 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. 5

6 26. Which one of the following is the best representation of the titration curve which will be obtained in the titration of a weak base (0.10 mol L -1 ) with HCl of the same concentration? 27. 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 HClO was titrated with 0.30 M NaOH. The following data was collected during the titration. ml NaOH added ph What is the K a for HClO? a b c d What volume of M KOH must be added to 17.5 ml of M H 3 PO 4 to reach the third equivalence point? a ml b ml c ml d ml 6

7 30. The solubility of aluminum hydroxide when dilute nitric acid is added to it. a. increases b. decreases c. does not change 31. The solubility of silver chloride when dilute nitric is added to it. a. increases b. decreases c. does not change 32. Write the ion product expression for magnesium fluoride, MgF 2. a. b. c. d. 33. Write the ion product expression for calcium phosphate, Ca 3 (PO 4 ) 2. a. b. c. d. 34. The solubility of lead(ii) chloride is 0.45 g/100 ml of solution. What is the K sp of PbCl 2? a b c d

8 35. The solubility of magnesium phosphate is g/1.0 L of solution. What is the K sp for Mg 3 (PO 4 ) 2? a b c d Calculate the solubility of barium carbonate, BaCO 3, in pure water. K sp = a M b M c M d M 37. Calculate the solubility of lead(ii) iodide, PbI 2, in M KI. K sp = a M b M c M d M 8