Name: Class: Date: Practice test Chapters 15 and 16: Acids and Bases 1. Which of the following pairs of species is not a conjugate acid base pair? A) HOCl, OCl B) HNO 2, NO + 2 C) O 2, OH D) HSO 4, SO 2 4 E) H 2 CO 3, HCO 3 2. Which of the following is the strongest acid? A) HClO 2 B) HCl C) HClO 4 D) HClO E) HClO 3 3. The concentration of H 3 O + in a solution is 7 10 4 M at 25 C. What is its hydroxide-ion concentration? A) 7 10 4 M B) 1 10 10 M C) 2 10 10 M D) 3 10 10 M E) 1 10 11 M 4. What is the ph of a 0.051 M HClO 4 solution? A) 15.29 B) 2.98 C) 12.71 D) 1.29 E) 11.02 5. A solution has a poh of 5.36. What is its hydroxide-ion concentration? A) 1.8 10 4 M B) 5.4 M C) 2.3 10 9 M D) 4.4 10 6 M E) 4.7 10 3 M 1
Name: 6. Consider the K a values for the following acids: Cyanic acid, HOCN, 3.5 10 4 Formic acid, HCHO 2, 1.7 10 4 Lactic acid, HC 3 H 5 O 3, 1.3 10 4 Propionic acid, HC 3 H 5 O 2, 1.3 10 5 Benzoic acid, HC 7 H 5 O 2, 6.3 10 5 Which has the strongest conjugate base? A) propionic acid B) benzoic acid C) lactic acid D) formic acid E) cyanic 7. At a temperature of 25 C an initally 0.048 M solution of a weak monoprotic acid is 2.7 % ionized once equilibrium is established. What is the acid-ionization constant, K a, for this acid? (assume C a /K a 3 10 2 ) A) 3.5 10 5 B) 1.7 10 6 C) 2.3 10 1 D) 1.5 10 2 E) 1.7 10 7 8. The equilibrium hydronium ion concentration of an initially 0.150 M solution of a monoprotic weak acid is 1.4 10 3 M. The acid dissociation constant is 1.31 10 5 at 25 C. What is the ph of this solution? A) 2.85 B) 7.00 C) 11.15 D) 5.71 E) 0.82 9. Which of the following reactions is associated with the definition of K b? A) CN (aq) + H + (aq) HCN(aq) B) F (aq) + H 2 O(l) HF(aq) + OH (aq) C) Zn(OH 2 ) 2+ 6 (aq) [Zn(OH 2 ) 5 OH] + (aq) + H + (aq) D) Cr 3+ (aq) + 6H 2 O(l) Cr(OH 2 ) 3+ 6 (aq) E) none of these 2
Name: 10. What is the ph of a 0.24 M solution of methylamine (CH 3 NH 2, K b = 4.4 10 4 ) at 25 o C? A) 5.63 B) 0.62 C) 12.00 D) 13.38 E) 2.00 11. Which of the following salts is most likely to form an aqueous solution having the ph shown in the figure below? A) NH 4 Cl B) NaBr C) K 2 CO 3 D) RbCN E) LiNO 3 12. What is K a at 25 C for the following equilibrium? C 6 H 5 NH 3+ (aq) + H 2 O(l) C 6 H 5 NH 2 (aq) + H 3 O + (aq) K b (C 6 H 5 NH 2 ) = 4.2 10 10 at 25 C. A) 4.2 10 4 B) 2.4 10 3 C) 4.2 10 10 D) 4.2 10 4 E) 2.4 10 5 13. Suppose a buffer solution is made from formic acid (HCHO 2 ) and sodium formate (NaCHO 2 ). What is the net ionic equation for the reaction that occurs when a small amount of hydrochloric acid is added to the buffer? A) H 3 O + (aq) + HCHO 2 (aq) H 2 O(l) + H 2 CHO 2+ (aq) B) H 3 O + (aq) + CHO 2 (aq) HCHO 2 (aq) + H 2 O(l) C) HCl(aq) + CHO 2 (aq) HCHO 2 (aq) + Cl (aq) D) HCl(aq) + OH (aq) H 2 O(l) + Cl (aq) E) H 3 O + (aq) + OH (aq) 2H 2 O(l) 3
Name: 14. What is the hydrogen-ion concentration of a solution that is 0.052 M in acetic acid and 0.052 M in sodium acetate at 25 C? The acid-ionization constant of acetic acid is 1.8 10 5 at 25 C. A) 1.8 10 3 M B) 1.8 10 6 M C) 1.8 10 7 M D) 1.8 10 5 M E) 1.8 10 4 M 15. What is the hydronium-ion concentration of a solution that is formed by combining 600. ml of 0.10 M NaOH with 400. ml of 0.80 M HNO 3 at 25 C? A) 0.080 M B) 0.010 M C) 0.80 M D) 0.45 M E) 0.26 M 4
Name: Record your response on your answer sheet. (White area of full size scantron) CLEARLY SHOW THE METHOD USED AND THE STEPS INVOLVED IN ARRIVING AT YOUR ANSWERS. It is to your advantage to do this, since you may obtain partial credit if you do and you will receive little or no credit if you do not. Attention should be paid to significant figures. This section of the exam should take approximately 20 minutes to complete 16. 5
Practice test Chapters 15 and 16: Acids and Bases Answer Section 1. ANS: B PTS: 1 DIF: easy REF: 15.2 OBJ: Identify acid and base species. (Example 15.1) TOP: acids and bases acid-base concepts KEY: Brønsted-Lowry concept of acids and bases 2. ANS: C PTS: 1 DIF: easy REF: 15.5 OBJ: Understand the rules for determining the relative strengths of oxoacids. TOP: acids and bases acid and base strength KEY: molecular structure and acid strength 3. ANS: E PTS: 1 DIF: easy REF: 15.7 OBJ: Calculate the concentrations of H3O+ and OH in solutions of a strong acid or base. (Example 15.4) TOP: acids and bases solutions of a strong acid or base 4. ANS: D PTS: 1 DIF: easy REF: 15.8 OBJ: Calculate the ph from the hydronium-ion concentration. (Example 15.5) TOP: acids and bases solutions of a strong acid or base KEY: ph of a solution 5. ANS: D PTS: 1 DIF: easy REF: 15.8 OBJ: Calculate the hydronium-ion concentration from the ph. (Example 15.6) TOP: acids and bases solutions of a strong acid or base KEY: ph of a solution 6. ANS: A PTS: 1 DIF: easy REF: 16.1 OBJ: Define acid-ionization constant and degree of ionization. TOP: acids and bases acid and base strength 7. ANS: A PTS: 1 DIF: easy REF: 16.1 OBJ: Define acid-ionization constant and degree of ionization. 8. ANS: A PTS: 1 DIF: easy REF: 16.1 OBJ: Calculate concentrations of species in a weak acid solution using Ka (approximation method). (Example 16.2) 9. ANS: B PTS: 1 DIF: easy REF: 16.3 OBJ: Define base-ionization constant. KEY: base-ionization equilibria 10. ANS: C PTS: 1 DIF: easy REF: 16.3 OBJ: Calculate concentrations of species in a weak base solution using Kb. (Example 16.5) KEY: base-ionization equilibria 1
11. ANS: A PTS: 1 DIF: easy REF: 16.4 OBJ: Predict whether a salt solution is acidic, basic, or neutral. (Example 16.6) KEY: acid-base properties of salt solutions prediction of salt solution acid-base properties 12. ANS: E PTS: 1 DIF: easy REF: 16.4 OBJ: Obtain Ka from Kb or Kb from Ka. (Example 16.7) KEY: acid-base properties of salt solutions 13. ANS: B PTS: 1 DIF: easy REF: 16.6 OBJ: Describe the ph change of a buffer solution with the addition of acid or base. with another solute KEY: buffer adding an acid or base to a buffer 14. ANS: D PTS: 1 DIF: easy REF: 16.6 OBJ: Calculate the ph of a buffer from given volumes of solution. (Example 16.11) with another solute KEY: buffer ph of a buffer 15. ANS: E PTS: 1 DIF: easy REF: 16.7 OBJ: Calculate the ph of a solution of a strong acid and a strong base. (Example 16.13) TOP: acids and bases solutions of a strong acid or base 2
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