CN-(aq) + H2O (l)
HCN(aq) + OH-(aq)Kb = 2.5 x 10-5
CH3NH2(aq) + H2O(l)
CH3NH3+(aq)
+ OH-(q)Kb = 5.0 x 10-4.
Chapter 17: Principles of Reactivity: Acids and Bases-page 741:
17.8 If you have 0.1M solutions of each of the following Bronsted bases, in
which solution is the hydroxide ion concentration larger? In which solution is the
pH higher?
CN-(aq) + H2O (l) HCN(aq) + OH-(aq)
Kb = 2.5 x 10-5
CH3NH2(aq) + H2O(l) CH3NH3+(aq)
+ OH-(q)
Kb = 5.0 x 10-4.
17.13. Write the formula and give the name of the conjugate acid of each of
the following bases:
(a) NH3
(b) HCO3-
(c) HS-
(d) Br-
(e) HSO4-
17.21. In each of the following acid-base reactions, identify the Bronsted
acid and base on the left, and their conjugate partners on the right.
(a) CH3CO2H(aq) + C5H5N(aq) CH3CO2-(aq)
+ C5H5NH+(aq)
(b) N2H4(aq) + HSO4-(aq) N2H5+(aq)
+ SO42-(aq)
(c) [Al(H2O)6]3+(aq) + OH-(aq) [Al(H2O)5OH]2+(aq)
+ H2O(l)
17.32. A certain table wine has a pH of 3.40. What is the hydronium ion concentration of the wine? Is it acidic or basic?
17.33. Milk of magnesia has a pH of 10.5. What is the hydronium ion concentration of the solution? What is the hydroxide ion concentration? Is the solution acidic or basic?
17.37. The pH of a solution of Ba(OH)2 is 10.66 at 25ºC. What is the hydroxide ion concentration in the solution? If the solution volume is 250.mL, how many grams of Ba(OH)2 must have been dissolved?
17.42. A 0.015 M solution of hydrogen cyanate, HOCN, has a pH of 2.67.
(a) What is the hydronium ion concentration in the solution?
(b) What is the ionization constant Ka for the acid?
17.49. Phenol, C6H5OH, is a weak organic acid.
C6H5OH(aq) + H2O(l) C6H5O-(aq)
+ H3O+(aq)
Ka = 1.3 x 10-10
Although somewhat toxic to humans, it is used as a disinfectant and in the manufacture
of plastics. If you dissolve 0.780 g of the acid in enough water to make 500.mL of
solution, what is the equilibrium hydronium ion concentration? What is the pH of
the solution?
17.70. Sulfurous acid, H2SO3, is weak acid capable of
providing two H+ ions.
(a) What is the pH of a 0.45 M solution of H2SO3?
(b) What is the equilibrium concentration of the sulfite ion, SO32-,
in the 0.45 M solution of H2SO3?
17.71. Ascorbic acid (vitamin C, C6H8O6) is a diprotic acid (Kal = 6.8 x 10-5 and Ka2 = 2.7 x 10-12). What is the pH of a solution that contains 5.0 mg of acid per milliliter of solution?
17.75. Decide if each of the following substances should be classified as a
Lewis acid or a Lewis base?
(a) BCl3
(b) H2N - NH2, hydrazine
(c) CN- in the reaction
Au+(aq) + 2 CN-(aq) [Au(CN)2]-(aq)
(d) Fe3+
17.96. Given the following solutions:
0.1 M NH3 0.1 M NH4Cl
0.1 M Na2CO3 0.1 M NaCH3CO2
(sodium acetate)
0.1 M NaCl 0.1 M NH4CH3CO2
(ammonium acetate)
0.1 M CH3CO2H
(a) Which of the solutions are acidic?
(b) Which of the solutions are basic?
(c) Which of the solutions is most acidic?
17.101. Nicotine, C10H14N2, has two basic
nitrogen atoms, and both can react with water to give a basic solution.
Nic(aq) + H2O(l) NicH+(aq) + OH-(aq)
NicH+(aq) + H2O(l) NicH2+(aq) + OH-
Kb1 is 7.0 x 10-7 and Kb2 is 1.1 x 10-10.
Calculate the approximate pH of the 0.020 M solution.
