Back
- The active ingredient in aspirin is acetylsalicylic acid 1HC9H7O42, a monoprotic acid with Ka = 3.3 * 10^-4 at 25 °C. What is the pH of a solution obtained by dissolving two extra-strength aspirin tablets, each containing 500 mg of acetylsalicylic acid, in 250 mL of water?
Problem 62
- Calculate the percent ionization of hydrazoic acid (HN3) in solutions of each of the following concentrations (Ka is given in Appendix D): (a) 0.400 M, (b) 0.100 M, (c) 0.0400 M.
Problem 63
Problem 64
Calculate the percent ionization of propionic acid (C2H5COOH) in solutions of each of the following concentrations (Ka is given in Appendix D): (a) 0.250 M (b) 0.0800 M (c) 0.0200 M
Problem 65
Citric acid, which is present in citrus fruits, is a triprotic acid (Table 16.3). (a) Calculate the pH of a 0.040 M solution of citric acid. (b) Did you have to make any approximations or assumptions in completing your calculations? (c) Is the concentration of citrate ion 1C6H5O7 3-2 equal to, less than, or greater than the H+ ion concentration?
- Tartaric acid is found in many fruits, including grapes, and is partially responsible for the dry texture of certain wines. Calculate the pH and the tartrate ion C4H4O6²⁻ concentration for a 0.250 M solution of tartaric acid, for which the acid-dissociation constants are listed in Table 16.3. Did you have to make any approximations or assumptions in your calculation?
Problem 66
- Consider the base hydroxylamine, NH2OH. (c) There are two atoms in hydroxylamine that have nonbonding electron pairs that could act as proton acceptors. Use Lewis structures and formal charges (Section 8.5) to rationalize why one of these two atoms is a much better proton acceptor than the other.
Problem 67
Problem 67a
Consider the base hydroxylamine, NH2OH. (a) What is the conjugate acid of hydroxylamine?
Problem 68a
The hypochlorite ion, ClO-, acts as a weak base. (a) Is ClO- a stronger or weaker base than hydroxylamine?
- Write the chemical equation and the Kb expression for the reaction of each of the following bases with water: (a) dimethylamine, (CH3)2NH (b) carbonate ion, CO3^2- (c) formate ion, CHO2^-
Problem 69
Problem 70a
Write the chemical equation and the Kb expression for the reaction of each of the following bases with water: (a) propylamine, C3H7NH2
- Calculate the molar concentration of OH- in a 0.075 M solution of ethylamine (C2H5NH2); Kb = 6.4 * 10^-4. Calculate the pH of this solution.
Problem 71
- Calculate the molar concentration of OH- in a 0.724 M solution of hypobromite ion BrO-; Kb = 4.0 * 10^-6. What is the pH of this solution?
Problem 72
Problem 73a
Ephedrine, a central nervous system stimulant, is used in nasal sprays as a decongestant. This compound is a weak organic base: C10H15ON1aq2 + H2O1l2 Δ C10H15ONH+1aq2 + OH-1aq2 A 0.035 M solution of ephedrine has a pH of 11.33. (a) What are the equilibrium concentrations of C10H15ON, C10H15ONH+, and OH-?
Problem 73b
Ephedrine, a central nervous system stimulant, is used in nasal sprays as a decongestant. This compound is a weak organic base: C10H15ON1aq2 + H2O1l2 Δ C10H15ONH+1aq2 + OH-1aq2 A 0.035 M solution of ephedrine has a pH of 11.33. (b) Calculate Kb for ephedrine.
Problem 74
Codeine 1C18H21NO32 is a weak organic base. A 5.0 * 10-3M solution of codeine has a pH of 9.95. Calculate the value of Kb for this substance. What is the pKb for this base?
Problem 76
Use the acid-dissociation constants in Table 16.3 to arrange these oxyanions from strongest base to weakest: SO42-, CO32-, SO32-, and PO43-.
Problem 77b
Which is the stronger base, the acetate ion or the hypochlorite ion?
Problem 77c
Calculate Kb values for CH3COO- and ClO-.
Problem 78a
Given that Kb for ammonia is 1.8 × 10-5 and that for hydroxylamine is 1.1 × 10-8, which is the stronger base?
Problem 78b
Which is the stronger acid, the ammonium ion or the hydroxylammonium ion?
- Using data from Appendix D, calculate [OH-] and pH for each of the following solutions: (a) 0.10 M NaBrO (b) 0.080 M NaHS (c) a mixture that is 0.10 M in NaNO2 and 0.20 M in Ca(NO3)2.
Problem 79
Problem 80b
Using data from Appendix D, calculate 3OH-4 and pH for each of the following solutions: (b) 0.035 M Na2S
Problem 82b
Pyridinium bromide 1C5H5NHBr2 is a strong electrolyte that dissociates completely into C5H5NH+ and Br-. An aqueous solution of pyridinium bromide has a pH of 2.95. (b) Using Appendix D, calculate the Ka for pyridinium bromide.
Problem 82c
Pyridinium bromide 1C5H5NHBr2 is a strong electrolyte that dissociates completely into C5H5NH+ and Br-. An aqueous solution of pyridinium bromide has a pH of 2.95. (c) A solution of pyridinium bromide has a pH of 2.95. What is the concentration of the pyridinium cation at equilibrium, in units of molarity?
Problem 83c
Predict whether aqueous solutions of the following compounds are acidic, basic, or neutral: (c) Na2CO3
Problem 84a
Predict whether aqueous solutions of the following substances are acidic, basic, or neutral: (a) AlCl3
Problem 84b
Predict whether aqueous solutions of the following substances are acidic, basic, or neutral: (b) NaBr
Problem 84e
Predict whether aqueous solutions of the following substances are acidic, basic, or neutral: (e) Na2SO3.
Problem 85
An unknown salt is either NaF, NaCl, or NaOCl. When 0.050 mol of the salt is dissolved in water to form 0.500 L of solution, the pH of the solution is 8.08. What is the identity of the salt?
Problem 86
An unknown salt is either KBr, NH4Cl, KCN, or K2CO3. If a 0.100 M solution of the salt is neutral, what is the identity of the salt?