Review Unit 9 Test (Chp 16): Acid-Base Equilibria
Name______Date:______Period:______
Review Unit 9 Test (Chp 16): Acid-Base Equilibria
1.A base is a substance that ______.
2.A Brønsted-Lowry acid is defined as a substance that ______.
3.All of the following species can function as Brønsted-Lowry bases in solution EXCEPT
(A) H2O
(B) NH3
(C) S2–
(D) NH4+
(E) HCO3–
F–(aq) + H2O(l) HF(aq) + OH–(aq)
4.Which of the following species, if any, acts as a Brønsted-Lowry base in the equilibrium above?
(A)HF(aq)
(B)H2O(l)
(C)F–(aq) only
(D)Both F–(aq) and OH–(aq) act as Brønsted-Lowry bases.
(E)No species acts as a Brønsted-Lowry base.
2 H2O H3O+ + OH–
5.In the autoionization reaction of water above, OH– acts as the ______of H2O.
6.The conjugate acid of HSO4– is ______and the conjugate base is ______.
7.What is the conjugate base of OH– ?
8.At 25˚C aqueous solutions with a pH of 8 have a hydroxide ion concentration, [OH–], of
(A) 1x10–14 M
(B) l x10–8 M
(C) l x10–6 M
(D) 1 M
(E) 8 M
9.In an aqueous solution with a pH of 11.50 at 25oC, the molar concentration of OH–(aq) is approximately ____ M.
(A) 3.2 x 10–12
(B) 3.2 x 10–3
(C) 2.5 x 10–1
(D) 2.5
(E) 3.2 x 10–11
10.The molar concentration of hydroxide ion in pure water at 25°C is ______.
11.Which of the following aqueous solutions has the highest [H3O+]?
(A)a solution with a pOH of 12.0
(B)pure water
(C)a 1 × 10–4 M solution of HNO3
(D)a solution with a pH of 3.0
(E)a 1 x 10–8 M solution of NaOH
12.Of the following, ______is a weak acid.
(A) HCl
(B) HNO3
(C) HClO4
(D) HF
(E) HBr
13.Which one of the following has the weakest conjugate base?
(A)HClO (Ka = 3.2 ×10–8)
(B)HF (Ka = 6.8 × 10–4)
(C)HNO2 (Ka = 4.5 × 10–4)
(D)HCN (Ka = 4.9 × 10–10)
(E)Acetic acid (Ka = 1.8 × 10–5)
14.Which of the following weak acids exhibits the highest percentage ionization?
(A)0.01 M HNO2 (Ka = 4.5 × 10–4)
(B)0.01 M HC2H3O2 (Ka = 1.8 × 10–5)
(C)0.01 M HClO (Ka = 3.2 × 10–8)
(D)0.01 M HF (Ka = 6.8 × 10–4)
(E)These will all exhibit the same percentage ionization.
15.Ascorbic acid, H2C6H6O6(aq), is a diprotic acid with K1 = 7.9x10–5 and K2 = 1.6x10–12.
In a 0.005 M aqueous solution of ascorbic acid, which of the following species is present in the lowest concentration?
(A)C6H6O62–(aq)
(B)HC6H6O6–(aq)
(C)H2C6H6O6(aq)
(D)H3O+(aq)
(E)H2O(l)
16.A 0.1 M aqueous solution of ______will have a pH of 7.0 at 25.0 °C.
NaOCl KBr NH4Cl Ca(C2H3O2)2
17.Of the following substances, an aqueous solution of ______will form basic solutions.
NH4Cl Cu(NO3)2 K2CO3 NaF
18.Kb for B– is 1 × 10–8. Ka for HB is ______.
19.The pH of a solution prepared by the addition of 100. mL of 0.02 M HCl(aq)
to 100. mL of distilled water is closest to _____.
Section II Free Response
Calculator Allowed
CLEARLY SHOW THE METHODS USED AND STEPS INVOLVED IN YOUR ANSWERS.
It is to your advantage to do this, because you may earn partial credit if you do and little or no credit if you do not. Attention should be paid to significant figures.
HC2H3O2(aq) H+(aq) + C2H3O2-(aq)
- Acetic acid, HC2H3O2, is a monoprotic acid that dissociates in solution, as represented by the equation above. Acetic acid is 0.347 percent dissociated in 1.50 M HC2H3O2(aq) at 298 K. For parts (a) and (b) below assume the temperature remains at 298 K.
(a) Write the expression for the acid-dissociation constant, Ka, for acetic acid and calculate its value. (3)
(b) Calculate the pH of 1.50 M HC2H3O2. (1)
CH3NH2(aq) + H2O(l) CH3NH3+(aq) + OH–(aq)
- Methylamine, CH3NH2, is a weak base that reacts according to the equation above. The value of the ionization constant, Kb, is 5.2510–4.
(a) Calculate the hydroxide ion concentration, [OH–], of a 0.225 M aqueous solution of methylamine. (2)
(b) A different sample of methylamine is dissolved in water at 50oC to produce 120.0 mL of a 0.450 M solution with a pH of 11.08. Calculate the equilibrium constant, Kb, for the reaction at 50oC. (3)
Ka = [H3O+][OCl–] = 3.2 x 10–8
[HOCl]
- Hypochlorous acid, HOCl, is a weak acid in water. The Ka expression for HOCl is shown above.
(a) Write a chemical equation showing how HOCl behaves as an acid in water.
(b) Calculate the pH of a 0.175 M solution of HOCl.
The nitrite ion, NO2–, reacts with water to form nitrous acid and hydroxide ion, as shown in the following equation.
NO2–(aq) + H2O(l) HNO2(aq) + OH–(aq)
(c) Given that [OH–] is 8.42 x 10–3 M in a 0.525 M solution of sodium nitrite, calculate each of the following.
(i) The value of Kb for the nitrite ion, NO2–(aq).
(ii) The value of Ka for nitrous acid, HNO2(aq).
(iii) Which acid is stronger, hypochlorous acid or nitrous acid? Justify your answer.
Beaker 1 Beaker 2 Beaker 3
0.010 M CH3COOH 0.010 M CH3COONa 0.010 M NaOH
- Each of the three beakers contains 50.0 mL of 0.010 M solution of CH3COOH, CH3COONa, or NaOH as shown above. Each solution is at 25oC.
(a) Determine the pH of the solution in beaker 3. Justify your answer. (1)
(b) In beaker 1, the reaction CH3COOH(aq) + H2O(l) H3O+(aq) + CH3COO–(aq) occurs.
The value of Ka for CH3COOH(aq) is 1.8 x 10–5 at 25oC.
(i) Write the Ka expression for the reaction of CH3COOH(aq) with H2O(l). (1)
(ii) Calculate the [H3O+] in the solution in beaker 1. (2)
(c) In beaker 2, the reaction CH3COO–(aq) + H2O(l) CH3COOH(aq) + OH–(aq) occurs.
(i) Calculate the Kb for CH3COO–(aq) at 25oC. (1)
(ii) The contents of beaker 1 are poured into beaker 2 and the resulting solution is stirred. Assume that volumes are additive. Calculate the pH of the resulting solution. (2)
ANSWER KEY
FR
- 2002B#1(a)(b)(modified with different values and substances)
- 2003#1(a)(b)(modified with 1993 A (ACID BASE))
- 2005#1(a)(b)(d)(modified with different values and substances)
- 2011#1(a)(b)(c)(modified with different values and substances)
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