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NONE OF THE MULTIPLE CHOICE PROBLEMS REQUIRES EXTENSIVE OR TIME COMSUMING CALCULATIONS. IF YOUR METHOD REQUIRES EXTENSTIVE CALCULATIONS IT IS EITHER WRONG OR HARDER THAN WHAT IS REQUIRED. 1. A 0.1 M solution of each acid in the table is prepared. Which has the HIGHEST ph. Careful. a. Acetic b. Fluoroacetic c. Formic d. Hydrocyanic e. Hydrofluoric 2. 2.5 g NaOH is diluted to 5.0 L. What is the ph? a. 1.90 b. 12.1 c. 0.30 d. 13.7 e. 13.17 3. 100.0 ml of 0.45 M HNO 3 is mixed with 200. ml of 0.55 M HCN? What is the ph? a. 0.00 b. 0.26 c. 0.35 d. 0.48 e. 0.82 4. 60.0 ml of 0.30 M HNO 3 is mixed with 40. ml of 0.20 M HCl? What is the ph? a. 0.74 b. 0.59 c. 0.93 d. 1.10 e. 0.52
5. 15.0 ml of 0.62 M HCl is mixed with 80. ml of 0.10 M KOH. What is the ph? a. 1.86 b. 1.79 c. 1.06 d. 1.01 e. >10 6. What is the hydrogen ion concentration of a 0.77 M HF? K a = 6.76 x 10-4 M. a. < 0.01 M b. 0.011 M c. 0.022 M d. 0.68 M e. 0.77 M 7. A 0.0019 M solution of a weak acid, HB, has a ph of 3.30. What is K a? a. 1.8x10-4 M b. 1.3x10-4 M c. 2.5x10-7 M d. >10-2 M e. <10-8 M 8. Which of the following ions is neutral? a. Al 3+ + d. NH 4 b. Br - e. CBr 3 COO - c. F -
9. H 2 B (B = conjugate base) is a diprotic acid. A solution of 0.23 M KHB is prepared. Is it acidic, basic, or neutral? + 6 HBaq + HOaq HO aq + HB aq K = 510 x ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) 2 2 3 a1 HB aq + H O aq H O aq + B aq K = 2x10 + 2 9 2 3 a2 a. Neutral because K a and K b for HB - = 2x10-9. b. Acidic because K + is an acidic ion. c. Acidic because K a for HB - = 5x10-6 > K b for HB - = 2x10-9 d. Basic because K a for HB - = 2x10-9 < K b for HB - = 5x10-6 10. 100. ml of 0.30 M acetic acid is added to 200 ml of 0.40 M sodium acetate. What is the ph? K a = 1.74 x 10-5. a. 4.33 b. 5.19 c. 4.64 d. 4.88 e. 4.76 11. Hydoxylanime (NH 2 OH) is a weak base like ammonia. K b = 1.07x10-8 and pk b = 7.97. It can be used to prepare a buffer solution whose ph is 6.30. If the NH 2 OH concentration is 0.400 M, what is the required NH 3 OH + concentration? Careful! a. < 0.1 M b. 0.305 M c. 0.215 M d. 0.745 M e. > 5 M 12. Buffers neutralize both acids and bases. When HBr is added to a buffer solution consisting of Sodium cyanide (NaCN) and hydrocyanic acid (HCN), which reaction (when completed) shows the neutralization of the acid? a. H 3 0 + (aq) +CN - (aq) b. H 3 0 + (aq) + Na + (aq) c. H 3 0 + (aq) + Br - (aq) d. H 3 0 + (aq) + HCN(aq) e. None of the above
13. 155 ml of 0.20 M HCl is added to 60.0 ml of 0.75 M NaCH 3 COO. What is the ph of the resulting solution? (K a = 1.74 x 10-5 M for acetic acid.) a. 5.11 b. 5.33 c. 4.76 d. 4.19 e. 4.41 ( ) ( ) HO aq + CHCOO aq + 3 3 14. What is the ph of 0.55 M NaF. K a for HF is 6.76 x 10-4. a. 0.26 b. 1.71 c. 1.72 d. 4.59 e. 13.74 15. In which of the following reactions does the underlined compound act as a either a BrØnsted- Lowry or Lewis base? (Note, I and II are different reactions.) I. HCO + H O H CO + OH 3 2 2 3 II. HCO + H O CO + H O 2 + 3 2 3 3 ( ) ( ) III. PH + B OH PH B OH where the P is bonded to the B 3 3 3 3 (a) only I (b) only II (c) only III (d) I and II (e) I, II, and III 16. Which of the following solutions is not a buffer solution? a. 0.1 M acetic acid and 0.5 M conjugate base. b. 0.3 M Fe(H 2 O) 3+ 6 and 0.3 M Fe(H 2 O) 5 OH 2+ d. 0.2 M N(CH 3 ) and 1.4 M NH(CH 3 ) + e. 0.55 M H + - and 0.60 M NO 3
PROBLEMS (12 POINTS EACH) I. (a) The magnitude of the K sp of Fe(OH) 2 is 1.0 x 10-15 at room temperature. (2 PTS) Write the solubility reaction or the solubility product expression (K sp =?): (b) (5 PTS) What is the solubility of Fe(OH) 2 in pure water at room temperature in mol/l? USE CORRECT NUMBER OF SIGNIFICANT FIGURES. (c) (5 PTS) What is the solubility of Fe(OH) 2 in a solution buffered to a ph of 11 at 25ºC?
II. 35 ml of a KCN are titrated with 0.250 M HCl. (a) (3 PTS) What is the neutralization reaction? (b) (3 PTS) It takes 22.0 ml of the acid to reach the equivalence point (to neutralize all of the base). What was the initial concentration of KCN? (c) (3 PTS) After 11.0 ml of acid are added to the original solution the ph is 9.32. What is K b for CN -? Hint, what is CN - converted to? (d) (3 PTS) What is the ph after 30 ml of acid are added to the original 35 ml of KCN?
III. Pot-pourri (a) (3 PTS) A solution of Pb(CH 3 COO) 2 is added to a solution of NaI. A yellow precipitate forms. What is it? + (b) (3 PTS) ( ) ( ) ( ) HO l H aq OH aq H 2 + > 0 7. What is the ph of pure water just above freezing? Explain why.. At room temperature the ph of pure water is (c) (4 PTS) The solubility product constant, K sp, of Ca(OH) 2 is 5.0 x10-6 M 2. 15 ml of 0.070 M Ca(NO 3 ) 2 is added to 40. ml of a buffer solution having a ph of 12.00. What is Q? Careful. (d) (2 PTS) In the last problem, does a precipitate form? Why? (No credit without proper justification--just a few words.)