CJ Bianconi Chem102 Spring 2015 Mock Exam 3 1. According to Bronsted-Lowry, acids are: a. Illegal hallucinogens. b. Substances that are sour. c. Substances that produce H3O+ when added to water. d. Substances that donate protons. 2. Cations can be: a. Acidic b. Basic c. Neutral d. A + B e. A + C 3. Hydroxide is: a. The conjugate base of water. b. The conjugate acid of water. c. The conjugate base of hydronium. d. The conjugate acid of hydronium. 4. A buffer: a. Is effective over the range Ka ± 1. b. Resists all pH change attempted. c. Can be made with a strong acid and a weak base. d. All of the above. e. A + B 5. A low pOH: a. Results only from a weak acid. b. Results only from a strong acid. c. Results only from a buffer solution. d. Indicates a high pH. 6. What is the name of a compound that can act as an acid or a base? a. Acibasic b. Amphoscopic c. Amphiprotic d. Ampharos 7. 14 = a. –log[pH] + -log[pOH] b. –log(Kw) c. Ka x Kb d. pH x pOH 8. When does the pH of a buffer equal the pKa of the buffer? a. Never. b. Only if the solution is composed of a weak acid and its conjugate weak base. c. When both conjugates are present in equal amounts. d. The pH of a buffer is always equal to its pKa. CJ Bianconi Chem102 Spring 2015 9. The conjugates of all strong acids and bases are __________ (except for the one exception) because __________. a. Strong; they are strong electrolytes. b. Weak; strong electrolytes neutralize to become weak electrolytes. c. Weak; the reverse reaction occurs to reform the original compound. d. Neutral; the reverse reaction does not occur in observable amounts. 10. If my buffer system of HF (Ka = 6.7 x 10-4) has a pOH of 10.83: a. The buffer solution can neutralize acid better than base. b. The buffer solution can neutralize base better than acid. c. The buffer solution can neutralized acid and base equally. d. This buffer cannot have the given pOH. 11. The conjugate base of HPO42- is: a. H3PO4 b. H2PO4c. PO43d. HPO42- has no conjugate base. 12. Which of the following theoretical acids is the strongest? a. HX, with a Ka of 5.0 • 10-3 b. HY, with a Ka of 1.8 • 10-8 c. HZ, with a Ka of 9.5 • 10-5 13. Using information from the question above, which of the following is true? a. Only two of the above acids could be used to make a buffer. b. Z- is a stronger base than X-. c. Y- has a pKb of 5.6 • 10-7. d. HX is a poor proton donor. 14. Which of the following mixtures could be used to make a buffer with pH = 3.10? a. HX/X- (Ka = 5.0 • 10-3) b. HY/Y- (Ka = 1.8 • 10-8) c. HZ/Z- (Ka = 9.5 • 10-5) d. 2 of the mixtures could be used. e. All of the mixtures could be used. 15. A solution of HZ/Z- is found at pH = 5.50. Which of the following is true? a. The solution is a buffer that is better at neutralizing added acid. b. The solution is a buffer that is better at neutralizing added base. c. The solution is a buffer that can neutralize acid or base equally. d. The solution is not an effective buffer. CJ Bianconi Chem102 Spring 2015 16. For the next substances, identify if the following is a strong acid, weak acid, neutral, weak base, or strong base. a. CH3NH3Br Weak Acid b. Ag2+ Neutral c. CH3COOH Weak Acid d. HNO2 Weak Acid e. SO2 Neutral f. CuCl3 Weak Acid g. Ba(OH)2 Strong Base h. NO3 Neutral i. KF Weak Base 2+ j. Ca Neutral k. HI Strong Acid l. C6H5NH2 Weak Base m. AlBr3 Weak Acid n. HNO3 Strong Acid 2o. SO3 Weak Base p. Mg(OH)2 Weak Base q. H2S Weak Acid r. LiI Neutral s. K2SO4 Weak Base t. Co2+ Weak Acid u. BeCl2 Weak Acid v. NH4NO3 Weak Acid w. ZnClO4 Weak Acid x. Sr2+ Neutral y. H2O Neutral 3+ z. Fe Weak Acid 17. Calculate the pH of each of these solutions, and label them as acidic, basic, or neutral. a. pH = 5.43 pH = 5.43 Acidic -2 b. [OH ] = 3.44 • 10 pH = 12.54 Basic c. pH = 7.00 pH = 7.00 Neutral d. pOH = -0.55 pH = 14.55 Basic e. [H3O+] = 1.8 • 10-5 pH = 4.74 Acidic f. [OH ] = 4.00 pH = 14.60 Basic g. pH = 3.12 pH = 3.12 Acidic h. pOH = 10.88 pH = 3.12 Acidic + -11 i. [H3O ] = 7.77 • 10 pH = 10.11 Basic + -6 j. [H3O ] = 1.21 • 10 pH = 5.92 Acidic CJ Bianconi Chem102 Spring 2015 18. For the following compounds, list another compound that could be added to it in order to create a buffer. If there are no compounds that could make a buffer with the listed one, write “DNE”. a. NH3 + an ionic compound with NH4+ or a strong acid b. CH3COOH + an ionic compound with CH3COO- or a strong base c. HF + an ionic compound containing F- or a strong base d. Na3PO4 + an ionic compound containing HPO42- or a strong acid e. NaI DNE f. KF + HF or a strong acid g. Ba(OH)2 + any weak acid h. HNO2 + an ionic compound with NO2- or a strong base i. MgCl2 DNE j. HCN + an ionic compound with CN- or a strong base 19. Identify if a buffer could be made from the following solutions. a. KOH + H2Se Yes, indirectly b. HBr + LiBr No c. HCN + NaCN Yes, directly d. HCl + NH3 Yes, indirectly e. LiOH + HI No f. CH3COOH + HNO3 No g. CH3NH3Cl + NaCl No h. H2SO3 + NaHSO3 Yes, directly i. CH4 + CH3OH No j. HNO3 + KNO3 No 20. Rank the following solutions in order from highest pH to lowest pH. a. 0.10 M C6H14 b. 0.10 M HCl c>a>b c. 0.10 M NH3 21. Rank the following solutions in order from lowest pOH to highest pOH. a. 12 M HNO3 b. 12 M BeCl2 b<c<a c. 12 M MgCl2 22. Rank the following solutions in order from highest pOH to lowest pOH. a. 0.5 M Ba(OH)2 b. 0.5 M AlBr3 a<c<b c. 0.5 M LiOH 23. What is the pH of a 0.0433 M NaOH solution? NaOH → Na+ + OH0.0433 M NaOH = 0.0433 M OH-log[OH-] = pOH = 1.36 14.00 – 1.36 = pH = 12.64 CJ Bianconi Chem102 Spring 2015 24. The pH of an equilibrated solution of weak acid is 2.13. If the initial concentration of the weak acid was 0.50 M, what is the value of the Ka for this acid? HA + H2O ↔ A- + H3O+ 0.50 0 0 -x x x 0.5-x x x [π΄− ][π»3 π+ ] (π₯)(π₯) πΎπ = = [π»π΄] (0.5 − π₯) -pH + 10 = [H3O ] = 0.007413 = x Ka = 1.16 • 10-4 25. A student measures the pH of a 0.84 M solution of weak acid to be 1.44. What is the value of the Ka for this acid? 26. What is the pH of a 560.0 mL solution containing 0.425 M HNO2 and 0.675 M KNO2? The Ka for HNO2 is 4.0 • 10-4. 27. What is the pH of the above solution after I add 30 mL of 1.83 M HNO3 to it?