The Ka? Kb Relationship; Acid–Base Properties of Salts

Problem 1PE Identifying Conjugate Acids and Bases (a) What is the conjugate base of HClO4, H2S, PH4+, HCO3- ? (b) What is the conjugate acid of CN- , SO42 - , H2O, HCO3- ? Write the formula for the conjugate acid of each of the following: HSO3 - , F- , PO4 3 - , CO.

(a) Identify the Brønsted–Lowry acid and base in the reaction (b) Identify the Lewis acid and base in the reaction. [Sections 16.2 and 16.11]

The following diagrams represent aqueous solutions of two monoprotic acids, HA (A = X or Y). The water molecules have been omitted for clarity. (a) Which is the stronger acid, HX or HY? (b) Which is the stronger base, X- o Y- ? (c) If you mix equal concentrations of HX and NaY, will the equilibrium HX(aq) + Y-(aq)?HY(aq) + X-(aq) lie mostly to the right (Kc > 1) or to the left (Kc < 1)? [Section 16.2]

Problem 2PE Writing Equations for Proton-Transfer Reactions The hydrogen sulfite ion (HSO3 - ) is amphiprotic. Write an equation for the reaction of HSO3 -with water (a) in which the ion acts as an acid and, (b) in which the ion acts as a base. In both cases identify the conjugate acid–base pairs. When lithium oxide (Li2O) is dissolved in water, the solution turns basic from the reaction of the oxide ion (O2-) with water. Write the equation for this reaction and identify the conjugate acid–base pairs.

The following diagrams represent aqueous solutions of three acids, HX, HY, and HZ. The water molecules have been omitted for clarity, and the hydrated proton is represented as H+ rather than H3O+. (a) Which of the acids is a strong acid? Explain. (b) Which acid would have the smallest acid dissociation constant, Ka? (c) Which solution would have the highest pH? [Sections 16.5 and 16.6]

Predicting the Position of a Proton-Transfer Equilibrium For the following proton-transfer reaction use Figure 16.3 to predict whether the equilibrium lies to the left (Kc < 1) or to the right (Kc > 1). HSO4-(aq) + CO32-(aq) SO42-(aq) + HCO3-(aq)

In which of the following cases is the approximation that the equilibrium concentration of H+(aq) is small relative to the initial concentration of HA likely to be most valid: (a) initial [HA] = 0.100 M and Ka = 1.0 x 10-6 (b) initial [HA] = 0.100 M and Ka = 1.0 x 10-4 (c) initial [HA] = 1.00 M and Ka = 1.0 x 10-6 ? [Section 16.6]

Problem 4PE Calculating [H+] for Pure Water Calculate the values of [H+] and [OH- ] in a neutral aqueous solution at 25 °C. Indicate whether solutions with each of the following ion concentrations are neutral, acidic, or basic: (a) [H+] = 4 × 10-9 M; (b) [OH-] = 1 × 10-7 M; (c) [OH-] = 1 × 10-13 M.

The indicator methyl orange has been added to both of these solutions. Based on the colors, classify each statement as true or false: (a) The pH of solution A is definitely less than 7.00. (b) The pH of solution B is definitely greater than 7.00. (c) The pH of solution B is greater than that of solution A. [Section 16.4]

Problem 5PE Calculating [H+] from [OH-] Calculate the concentration of H+(aq) in (a) a solution in which [OH-] is 0.010 M,, (b) a solution in which [OH-] is 1.8 × 10-9M. Note: In this problem and all that follow, we assume, unless stated otherwise, that the temperature is 25 °C. Calculate the concentration of OH- (aq) in a solution in which (a) [H+] = 2 × 10- 6 M; (b) [H+] = [OH-] (c) [H+] = 200 × [OH- ].

(a) Which of these three lines represents the effect of concentration on the percent ionization of a weak acid? (b) Explain in qualitative terms why the curve you chose has the shape it does. [Section 16.6]

Problem 6PE Calculating pH from [H+] Calculate the pH values for the two solutions of Sample Exercise. Calculating [H+] from [OH-] Calculate the concentration of H+(aq) in (a) a solution in which [OH-] is 0.010 M,, (b) a solution in which [OH-] is 1.8 × 10-9M. Note: In this problem and all that follow, we assume, unless stated otherwise, that the temperature is 25 °C. A solution has [OH-] = 4.0 × 10- 8. What is the value of [H+] for the solution? (a) 2.5 × 10- 8 M, (b) 4.0 × 10- 8 M, (c) 2.5 × 10- 7 M, (d) 2.5 × 10- 6 M, (e) 4.0 × 10- 6 M Calculating [H+] from [OH-] Calculate the concentration of H+(aq) in (a) a solution in which [OH-] is 0.010 M,, (b) a solution in which [OH-] is 1.8 × 10-9M. Note: In this problem and all that follow, we assume, unless stated otherwise, that the temperature is 25 °C. Calculate the concentration of OH- (aq) in a solution in which (a) [H+] = 2 × 10- 6 M; (b) [H+] = [OH-], (c) [H+] = 200 × [OH- ]. (a) In a sample of lemon juice, [H+] = 3.8 × 10-4 M. What is the pH? (b) A commonly available window-cleaning solution has [OH-] = 1.9 × 10-6 M. What is the pH at 25 °C?

Each of the three molecules shown here contains an OH group, but one molecule acts as a base, one as an acid, and the third is neither acid nor base. (a) Which one acts as a base? Why does only this molecule act as a base? (b) Which one acts as an acid? (c) Why is the remaining molecule neither acidic nor basic? [Sections 16.6 and 16.7]

A solution formed by dissolving an antacid tablet has a pH of 9.18. Calculate [OH-].

Which of the following diagrams best represents an aqueous solution of NaF? The water molecules are not shown for clarity. Will this solution be acidic, neutral, or basic? [Section 16.9]

Problem 8PE Calculating the pH of a Strong Acid What is the pH of a 0.040 M solution of HClO4? An aqueous solution of HNO3 has a pH of 2.34. What is the concentration of the acid?

Consider the molecular models shown here, where X represents a halogen atom. (a) If X is the same atom in both molecules, which one will be more acidic? (b) Does the acidity of each molecule increase or decrease as the electronegativity of the atom X increases? [Section 16.10]

What is the concentration of a solution of (a) KOH for which the pH is 11.89, (b) \(Ca(OH)_2\) for which the pH is 11.68?

(a) The following diagram represents the reaction of PCI4+ with CI-. Draw the Lewis structures for the reactants and products, and identify the Lewis acid and the Lewis base in the reaction. (b) The following reaction represents a hydrated cation losing a proton. How does the equilibrium constant for the reaction change as the charge of the cation increases? [Sections 16.9 and 16.11]

A student prepared a 0.10 M solution of formic acid (HCOOH) and found its pH at to be 2.38. Calculate Ka for formic acid at this temperature.

Problem 11E Although HCl and H2SO4 have very different properties as pure substances, their aqueous solutions possess many common properties. List some general properties of these solutions, and explain their common behavior in terms of the species present.

As calculated in Sample Exercise 16.10, a 0.10 M solution of formic acid (HCOOH) contains 4.2 X 10-3 MH+(aq). Calculate the percentage of the acid that is ionized.

Problem 12E Although pure NaOH and NH3 have very different properties, their aqueous solutions possess many common properties. List some general properties of these solutions, and explain their common behavior in terms of the species present.

Calculate the pH of a 0.20 M solution of HCN. (Refer to Table 16.2 or Appendix D for the value of Ka.)

Problem 13E Arrhenius and Brønsted–Lowry Acids and Bases (Sections) (a) What is the difference between the Arrhenius and the Brønsted–Lowry definitions of an acid? (b) NH3(g) and HCl(g) react to form the ionic solid NH4Cl(s). Which substance is the Brønsted–Lowry acid in this reaction? Which is the Brønsted–Lowry base?

Calculate the percentage of HF molecules ionized in (a) a 0.10 M HF solution, (b) a 0.010 M HF solution.

Problem 14E Arrhenius and Brønsted–Lowry Acids and Bases (Sections) (a) What is the difference between the Arrhenius and the Brønsted–Lowry definitions of a base? (b) Can a substance behave as an Arrhenius base if it does not contain an OH group? Explain.

Problem 15E Arrhenius and Brønsted–Lowry Acids and Bases (Sections) (a) Give the conjugate base of the following Brønsted–Lowry acids:(i) HIO3, (ii) NH4+. (b) Give the conjugate acid of the following Brønsted–Lowry bases: (i) O2-, (ii) H2PO4-.

The solubility of CO2 in water at 25°C and 0.1 atm is 0.0037 M. The common practice is to assume that all the dissolved CO2 is in the form of carbonic acid (H2CO3), which is produced in the reaction CO2(aq) + H2O(l) ? H2CO3(aq) What is the pH of a 0.0037 M solution of H2CO3?

Problem 15PE Using Kb to Calculate OH- Calculate the concentration of OH- in a 0.15 M solution of NH3. Which of the following compounds should produce the highest pH as a 0.05 M solution: pyridine, methylamine, or nitrous acid?

Problem 16E Arrhenius and Brønsted–Lowry Acids and Bases (Sections) (a) Give the conjugate base of the following Brønsted–Lowry acids: (i) HCOOH, (ii) HPO42-. (b)Give the conjugate acid of the following Brønsted–Lowry bases: (i) SO42-, (ii) CH3NH2.

Problem 17E Arrhenius and Brønsted–Lowry Acids and Bases (Sections) Designate the Brønsted–Lowry acid and the Brønsted–Lowry base on the left side of each of the following equations, and also designate the conjugate acid and conjugate base of each on the right side: (a) NH4+(aq) + CN-(aq) ? HCN(aq) + NH3(aq) ________________ (b) (CH3)3N(aq) + H2O(l) ? (CH3)3NH +(aq) + OH-(aq) ________________ (c) HCOOH(aq) + PO43-(aq)? HCOO-(aq) + HPO42-(aq)

A solution made by adding solid sodium hypochlorite (NaClO) to enough water to make 2.00 L of solution has a pH of 10.50. Using the information in Equation 16.37, calculate the number of moles of NaClO added to the water.

a) Which of these anions has the largest base-dissociation constant: \(NO_{2}^{-}, PO_{4}^{3-}, or N_{3}^{-}\)? (b) The base quinoline has the structure Its conjugate acid is listed in handbooks as having a \(pK_a\) of 4.90. What is the base-dissociation constant for quinoline?

Designate the Brønsted-Lowry acid and the Brønsted-Lowry base on the left side of each equation, and also designate the conjugate acid and conjugate base of each on the right side. (a) \(\mathrm{HBrO}(a q)+\mathrm{H}_2 \mathrm{O}(l) \rightleftharpoons \mathrm{H}_3 \mathrm{O}^{+}(a q)+\mathrm{BrO}^{-}(a q)\) (b) \(\mathrm{HSO}_4{ }^{-}(a q)+\mathrm{HCO}_3{ }^{-}(a q) \rightleftharpoons \mathrm{SO}_4{ }^{2-}(a q)+\mathrm{H}_2 \mathrm{CO}_3(a q)\) (c) \(\mathrm{HSO}_3^{-}(a q)+\mathrm{H}_3 \mathrm{O}^{+}(a q) \rightleftharpoons \mathrm{H}_2 \mathrm{SO}_3(a q)+\mathrm{H}_2 \mathrm{O}(l)\)

Problem 19E Arrhenius and Brønsted–Lowry Acids and Bases (Sections) (a) The hydrogen sulfite ion (HSO3?) is amphiprotic. Write a balanced chemical equation showing how it acts as an acid toward water and another equation showing how it acts as a base toward water. (b) What is the conjugate acid of HSO3 -? What is its conjugate base?

Predict whether the salt Na2HPO4 forms an acidic solution or a basic solution when dissolved in water.

Problem 20E Arrhenius and Brønsted–Lowry Acids and Bases (Sections) (a) Write an equation for the reaction in which H2C6H7O5 –(aq) acts as a base in H2O(l). (b)Write an equation for the reaction in which H2C6H7O5–(aq) acts as an acid in H2O(l). (c) What is the conjugate acid of H2C6H7O5–(aq)? What is its conjugate base?

Problem 21E Arrhenius and Brønsted–Lowry Acids and Bases (Sections) Label each of the following as being a strong base, a weak base, or a species with negligible basicity. In each case write the formula of its conjugate acid, and indicate whether the conjugate acid is a strong acid, a weak acid, or a species with negligible acidity: (a) CH3COO-, (b) HCO3-,(c) O2-, (d) Cl-, (e) NH3.

Problem 23E Arrhenius and Brønsted–Lowry Acids and Bases (Sections) (a) Which of the following is the stronger Brønsted–Lowry acid, HBrO or HBr? (b) Which is the stronger Brønsted–Lowry base, F- or Cl-?

Problem 24E Arrhenius and Brønsted–Lowry Acids and Bases (Sections) (a) Which of the following is the stronger Brønsted–Lowry acid, HClO3 or HClO2? (b) Which is the stronger Brønsted–Lowry base, HS- or HSO4-?

Label each of the following as being a strong acid, a weak acid, or a species with negligible acidity. In each case write the formula of its conjugate base, and indicate whether the conjugate base is a strong base, a weak base, or a species with negligible basicity: (a) HCOOH, (b) \(H_2\), (c) \(CH_4\), (d) HF, (e) \(NH_{4}^{+}\).

Predict the products of the following acid–base reactions, and predict whether the equilibrium lies to the left or to the right of the equation: (a) \(\mathrm{O}^{2-}(a q)+\mathrm{H}_{2} \mathrm{O}(l) \rightleftharpoons\) (b) \(\mathrm{CH}_{3} \mathrm{COOH}(a q)+\mathrm{HS}^{-}(a q) \rightleftharpoons\) (c) \(\mathrm{NO}_{2}^{-}(a q)+\mathrm{H}_{2} \mathrm{O}(l) \rightleftharpoons\)

Problem 26E Arrhenius and Brønsted–Lowry Acids and Bases (Sections) Predict the products of the following acid–base reactions, and predict whether the equilibrium lies to the left or to the right of the equation: (a) NH4+(aq) + OH-(aq) ? ________________ (b) CH3COO-(aq) + H3O+(aq) ? ________________ (c) HCO3-(aq) + F-(aq) ?

If a neutral solution of water, with pH = 7.00, is heated to 50 °C, the pH drops to 6.63. Does this mean that the concentration of [H+] is greater than the concentration of [H-]? Explain.

Problem 28E (a) Write a chemical equation that illustrates the autoionization of water. (b) Write the expression for the ion-product constant for water, Kw.Why is [H2O] absent from this expression? (c) A solution is described as basic. What does this statement mean?

Problem 29E Autoionization of Water (Section) Calculate [H+] for each of the following solutions, and indicate whether the solution is acidic, basic, or neutral: (a) [OH-] = 0.00045 M; (b) [OH-] = 8.8 × 10-9 M; (c) a solution in which [OH-] is 100 times greater than [H+].

Problem 30E Autoionization of Water (Section) Calculate [OH-] for each of the following solutions, and indicate whether the solution is acidic, basic, or neutral: (a) [H+] = 0.0505 M; (b) [H+] = 2.5 × 10-10 M; (c) a solution in which [H+] is 1000 times greater than [OH-].

Problem 31E Autoionization of Water (Section) At the freezing point of water (0 °C), Kw = 1.2 × 10-15. Calculate [H+] and [OH-] for a neutral solution at this temperature.

Problem 32E Autoionization of Water (Section) Deuterium oxide (D2O, where D is deuterium, the hydrogen-2 isotope) has an ion-product constant, Kw, of 8.9 × 10-16 at 20 °C. Calculate [D+] and [OD-] for pure (neutral) D2O at this temperature.

Problem 33E The pH Scale (Section) By what factor does [H+] change for a pH change of (a) 2.00 units, (b) 0.50 units?

Problem 34E The pH Scale (Section) Consider two solutions, solution A and solution B. [H+] in solution A is 250 times greater than that in solution B. What is the difference in the pH values of the two solutions?

(a) If NaOH is added to water, how does [H+] change? How does pH change? (b) Use the pH values in Figure 16.5 to estimate the pH of a solution with [H+] = 0.0006 M. Is the solution acidic or basic? (c) If the pH of a solution is 5.2, first estimate and then calculate the molar concentrations of H+ (aq) and OH-(aq) in the solution

(a) If HNO3 is added to water, how does [OH-] change? How does pH change? (b) Use the pH values in Figure 16.5 to estimate the pH of a solution with [OH-] = 0.014 M. Is the solution acidic or basic? (c) If pH = 6.6, first estimate and then calculate the molar concentrations of H+(aq) and OH- in the solution.

Complete the following table by calculating the missing entries and indicating whether the solution is acidic or basic.

Complete the following table by calculating the missing entries. In each case indicate whether the solution is acidic or basic.

Problem 39E The pH Scale (Section) The average pH of normal arterial blood is 7.40. At normal body temperature (37 °C), Kw = 2.4 × 10-14. Calculate [H+], [OH-], and pOH for blood at this temperature.

Problem 40E The pH Scale (Section) Carbon dioxide in the atmosphere dissolves in raindrops to produce carbonic acid (H2CO3), causing the pH of clean, unpolluted rain to range from about 5.2 to 5.6. What are the ranges of [H+] and [OH-] in the raindrops?

(a) What is a strong acid? (b) A solution is labeled 0.500 M HCl. What is [H+] for the solution? (c) Which of the following are strong acids: HF, HCl, HBr, HI?

(a) What is a strong base? (b) A solution is labeled 0.035 M Sr(OH)2. What is [OH-] for the solution? (c) Is the following statement true or false? Because Mg(OH)2 is not very soluble, it cannot be a strong base. Explain.

Problem 43E Strong Acids and Bases (Section) Calculate the pH of each of the following strong acid solutions: (a) 8.5 × 10-3M HBr, (b) 1.52 g of HNO3 in 575 mL of solution, (c) 5.00 mL of 0.250 M HClO4 diluted to 50.0 mL, (d) a solution formed by mixing 10.0 mL of 0.100 M HBr with 20.0 mL of 0.200 M HCl.

Problem 44E Strong Acids and Bases (Section) Calculate the pH of each of the following strong acid solutions: (a) 0.0167 M HNO3, (b) 0.225 g of HClO3 in 2.00 L of solution, (c) 15.00 mL of 1.00 M HCl diluted to 0.500 L, (d) a mixture formed by adding 50.0 mL of 0.020 M HCl to 125 mL of 0.010 M HI.

Problem 45E Strong Acids and Bases (Section) Calculate [OH-] and pH for (a) 1.5 × 10-3M Sr(OH)2, (b) 2.250 g of LiOH in 250.0 mL of solution, (c) 1.00 mL of 0.175 M NaOH diluted to 2.00 L, (d) a solution formed by adding 5.00 mL of 0.105 M KOH to 15.0 mL of 9.5 × 10-2 M Ca(OH)2.

Problem 46E Strong Acids and Bases (Section) Calculate [OH-] and pH for each of the following strong base solutions: (a) 0.182 M KOH, (b)3.165 g of KOH in 500.0 mL of solution, (c) 10.0 mL of 0.0105 M Ca(OH)2 diluted to 500.0 mL,(d) a solution formed by mixing 20.0 mL of 0.015 M Ba(OH)2 with 40.0 mL of 8.2 × 10-3 MNaOH.

Problem 48E Strong Acids and Bases (Section) Calculate the concentration of an aqueous solution of Ca(OH)2 that has a pH of 10.05.

Problem 47E Strong Acids and Bases (Section) Calculate the concentration of an aqueous solution of NaOH that has a pH of 11.50.

Problem 49E Weak Acids (Section) Write the chemical equation and the Ka expression for the ionization of each of the following acids in aqueous solution. First show the reaction with H+(aq) as a product and then with the hydronium ion:(a) HBrO2, ________________ (b) C2H5COOH.

Problem 50E Weak Acids (Section) Write the chemical equation and the Ka expression for the acid dissociation of each of the following acids in aqueous solution. First show the reaction with H+(aq) as a product and then with the hydronium ion: (a) C6H5COOH, (b) HCO3-.

Problem 51E Weak Acids (Section) Lactic acid (CH3CH(OH)COOH) has one acidic hydrogen. A 0.10 M solution of lactic acid has a pH of 2.44. Calculate Ka.

Problem 52E Weak Acids (Section) Phenylacetic acid (C6H5CH2COOH) is one of the substances that accumulates in the blood of people with phenylketonuria, an inherited disorder that can cause mental retardation or even death. A 0.085 M solution of C6H5CH2COOH has a pH of 2.68. Calculate the Ka value for this acid

Problem 53E Weak Acids (Section) A 0.100 M solution of chloroacetic acid (ClCH2COOH) is 11.0% ionized. Using this information, calculate [ClCH2COO-], [H+], [ClCH2COOH], and Ka for chloroacetic acid.

Problem 54E Weak Acids (Section) A 0.100 M solution of bromoacetic acid [BrCH2COOH] is 13.2% ionized. Calculate [H+], [BrCH2COO-], [BrCH2COOH] and Ka for bromoacetic acid.

Problem 55E Weak Acids (Section) A particular sample of vinegar has a pH of 2.90. If acetic acid is the only acid that vinegar contains (Ka = 1.8 × 10-5), calculate the concentration of acetic acid in the vinegar.

Problem 56E Weak Acids (Section) If a solution of HF (Ka = 6.8 × 10-4) has a pH of 3.65, calculate the concentration of hydrofluoric acid.

Problem 57E Weak Acids (Section) The acid-dissociation constant for benzoic acid (C6H5COOH) is 6.3 × 10-5. Calculate the equilibrium concentrations of H3O+, C6H5COO-, and C6H5COOH in the solution if the initial concentration of C6H5COOH is 0.050 M.

Problem 58E Weak Acids (Section) The acid-dissociation constant for chlorous acid (HClO2) is 1.1 × 10-2. Calculate the concentrations of H3O+, ClO2 -, and HClO2 at equilibrium if the initial concentration of HClO2 is 0.0125 M.

Problem 60E Weak Acids (Section) Determine the pH of each of the following solutions (Kaand Kb values are given in Appendix D):(a) 0.095 M hypochlorous acid, (b) 0.0085 M hydrazine, (c) 0.165 M hydroxylamine.

Calculate the pH of each of the following solutions (\(K_a\) and \(K_b\) values are given in Appendix D): (a) 0.095 M propionic acid \((C_2H_5COOH)\), (b) 0.100 M hydrogen chromate ion \((HCrO_{4}^{-})\), (c) 0.120 M pyridine \((C_5H_5N)\).

Problem 61E Weak Acids (Section) Saccharin, a sugar substitute, is a weak acid with pKa = 2.32 at 25 °C. It ionizes in aqueous solution as follows: HNC7H4SO3(aq) ? H+(aq) + NC7H4SO3–(aq) What is the pH of a 0.10 M solution of this substance?

Problem 62E Weak Acids (Section) The active ingredient in aspirin is acetylsalicylic acid (HC9H7O4), 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, containing 500 mg of acetylsalicylic acid each, in 250 mL of water?

Problem 63E Weak Acids (Section) 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 64E Weak Acids (Section) 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 65E Show that for a weak acid, the percent ionization should vary as the inverse square root of the acid concentration.

Problem 66E For solutions of a weak acid, a graph of pH versus the logarithm of the initial acid concentration should be a straight line. What is the magnitude of the slope of that line?

Citric acid, which is present in citrus fruits, is a triprotic acid (Table 16.3). Calculate the pH of a 0.040 M solution of citric acid. Explain any approximations or assumptions you make in your calculations. Is the concentration of citrate ion 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 tartarate ion \(\left(\mathrm{C}_{4} \mathrm{H}_{4} \mathrm{O}_{6}{ }^{2-}\right)\) concentration for a 0.250 M solution of tartaric acid, for which the acid-dissociation constants are listed in Table 16.3. Explain any approximations or assumptions that you make in your calculation.

Consider the base hydroxylamine, NH?OH. (a) What is the conjugate acid of hydroxylamine? (b) When it acts as a base, which atom in hydroxylamine accepts a proton? (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.

The hypochlorite ion, \(ClO^-\), acts as a weak base. (a) Is \(ClO^-\) a stronger or weaker base than hydroxylamine? (b) When \(ClO^-\) acts as a base, which atom, Cl or O, acts as the proton acceptor? (c) Can you use formal charges to rationalize your answer to part (b)?

Problem 71E Weak Bases (Section) 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, CO32-; (c) formate ion, CHO2-.

Problem 72E Weak Bases (Section) Write the chemical equation and the Kb expression for the reaction of each of the following bases with water: (a) propylamine, C3H7NH2; (b) monohydrogen phosphate ion, HPO42-; (c)benzoate ion, C6H5CO2-

Problem 73E Weak Bases (Section) 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 74E Weak Bases (Section) 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 75E Weak Bases (Section) Ephedrine, a central nervous system stimulant, is used in nasal sprays as a decongestant. This compound is a weak organic base: C10H15ON(aq) + H2O(l) ? C10H15ONH+(aq) + OH-(aq) A 0.035 M solution of ephedrine has a pH of 11.33. (a) What are the equilibrium concentrations of C10H15ON, C10H15ONH+, and OH-? (b) Calculate Kb for ephedrine.

Codeine \(\left(\mathrm{C}_{18} \mathrm{H}_{21} \mathrm{NO}_3\right)\) is a weak organic base. A \(5.0 \times 10^{-3} \mathrm{M}\) solution of codeine has a \(\mathrm{pH}\) of 9.95. Calculate the value of \(K_b\) for this substance. What is the \(\mathrm{p} K_b\) for this base?

Problem 77E The Ka? Kb Relationship; Acid–Base Properties of Salts (Sections) Although the acid-dissociation constant for phenol (C6H5OH) is listed in Appendix D, the base-dissociation constant for the phenolate ion (C6H5O-) is not. (a) Explain why it is not necessary to list both Ka for phenol and Kb for the phenolate ion. (b) Calculate Kb for the phenolate ion.(c) Is the phenolate ion a weaker or stronger base than ammonia?

Use the acid-dissociation constants in Table 16.3 to arrange these oxyanions from strongest base to weakest: and .

Problem 79E The Ka? Kb Relationship; Acid–Base Properties of Salts (Sections) (a) Given that Ka for acetic acid is 1.8 × 10-5 and that for hypochlorous acid is 3.0 × 10-8, which is the stronger acid? (b) Which is the stronger base, the acetate ion or the hypochlorite ion? (c) Calculate Kb values for CH3COO- and ClO-.

Using data from Appendix D, calculate \([OH^-]\) and pH for each of the following solutions: (a) 0.10M NaBrO, (b) 0.080 M NaHS, (c) a mixture that is 0.10 M in \(NaNO_2\) and 0.20 M in \(Ca(NO_2)_2\).

(a) Given that \(K_b\) for ammonia is \(1.8 \times 10^{-5}\) and that for hydroxylamine is \(1.1 \times 10^{-8}\), which is the stronger base? (b) Which is the stronger acid, the ammonium ion or the hydroxylammonium ion? (c) Calculate \(K_a\) values for \(\mathrm{NH}_4{ }^{+}\) and \(\mathrm{H}_3 \mathrm{NOH}^{+}\).

Using data from Appendix D, calculate \(\left[\mathrm{OH}^{-}\right]\) and pH for each of the following solutions: (a) 0.105 M NaF (b) 0.035 M \(\mathrm{Na}_2 \mathrm{~S}\), (c) a mixture that is 0.045 M in \(\mathrm{CH}_3 \mathrm{COONa}\) and 0.055 M in \(\left(\mathrm{CH}_3 \mathrm{COO}\right)_2 \mathrm{Ba}\).

Predict whether aqueous solutions of the following compounds are acidic, basic, or neutral: (a) \(\mathrm{NH}_{4} \mathrm{Br}\), (b) \(\mathrm{FeCl}_{3}\), (c) \(\mathrm{Na}_{2} \mathrm{CO}_{3}\), (d) \(\mathrm{KClO}_{4}\), (e) \(\mathrm{NaHC}_{2} \mathrm{O}_{4}\).

Problem 84E The Ka? Kb Relationship; Acid–Base Properties of Salts (Sections) Predict whether aqueous solutions of the following substances are acidic, basic, or neutral: (a)AlCl3, (b) NaBr, (c) NaClO, (d) [CH3NH3]NO3, (e) Na2SO3.

Problem 85E The Ka? Kb Relationship; Acid–Base Properties of Salts (Sections) 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 86E The Ka? Kb Relationship; Acid–Base Properties of Salts (Sections) 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?

Problem 87E How does the acid strength of an oxyacid depend on (a) the electronegativity of the central atom; (b) the number of non-protonated oxygen atoms in the molecule?

Problem 88E (a) Why is NH3 a stronger base than H2O? (b) Why is NH3 a stronger base than CH4?

Problem 89E Acid–Base Character and Chemical Structure (Section) Explain the following observations: (a) HNO3 is a stronger acid than HNO2; (b) H2S is a stronger acid than H2O; (c) H2SO4 is a stronger acid than HSO4-; (d) H2SO4 is a stronger acid than H2SeO4; (e) CCl3COOH is a stronger acid than CCl3COOH.

Problem 90E Acid–Base Character and Chemical Structure (Section) Explain the following observations: (a) HCl is a stronger acid than H2S; (b) H3PO4 is a stronger acid than H3AsO4; (c) HBrO3 is a stronger acid than HBrO2; (d) H2C2O4 is a stronger acid than HC2O4 -; (e) benzoic acid (C6H5COOH) is a stronger acid than phenol (C6H5OH).

Problem 91E Acid–Base Character and Chemical Structure (Section) Based on their compositions and structures and on conjugate acid–base relationships, select the stronger base in each of the following pairs: (a) BrO- or ClO-, (b) BrO- or BrO2-, (c) HPO42- or H2PO4-

Based on their compositions and structures and on conjugate acid-base relationships, select the stronger base in each of the following pairs: (a) \(\mathrm{NO}_3{ }^{-}\) or \(\mathrm{NO}_2{ }^{-}\), (b) \(\mathrm{PO}_4{ }^{3-}\) or \(\mathrm{AsO}_4{ }^{3-}\), (c) \(\mathrm{HCO}_3{ }^{-}\) or \(\mathrm{CO}_3{ }^{2-}\).

Problem 94E Acid–Base Character and Chemical Structure (Section) Indicate whether each of the following statements is true or false. For each statement that is false, correct the statement to make it true. (a) Acid strength in a series of H—A molecules increases with increasing size of A. (b) For acids of the same general structure but differing electronegativities of the central atoms, acid strength decreases with increasing electronegativity of the central atom. (c) The strongest acid known is HF because fluorine is the most electronegative element.

If a substance is an Arrhenius base, is it necessarily a Brønsted–Lowry base? Is it necessarily a Lewis base?

Problem 93E Acid–Base Character and Chemical Structure (Section) Indicate whether each of the following statements is true or false. For each statement that is false, correct the statement to make it true. (a) In general, the acidity of binary acids increases from left to right in a given row of the periodic table. (b) In a series of acids that have the same central atom, acid strength increases with the number of hydrogen atoms bonded to the central atom. (c) Hydrotelluric acid (H2Te) is a stronger acid than H2S because Te is more electronegative than S.

Problem 96E If a substance is a Lewis acid, is it necessarily a Brønsted–Lowry acid? Is it necessarily an Arrhenius acid?

Problem 97E Lewis Acids and Bases (Section) Identify the Lewis acid and Lewis base among the reactants in each of the following reactions: (a) Fe(ClO4)3(s) + 6 H2O(l) ? Fe(H2O)63+(aq) + 3 ClO4-(aq) ________________ (b) CN-(aq) + H2O(l) ? HCN(aq) + OH-(aq) ________________ (c) (CH3)3N(g) + BF3(g) ? (CH3)3NBF3(s) ________________ (d) HIO(lq) + NH2-(lq) ? NH3(lq) + IO-(lq) (lq denotes liquid ammonia as solvent)

Identify the Lewis acid and Lewis base in each of the following reactions: (a) \(\mathrm{HNO}_2(a q)+\mathrm{OH}^{-}(a q) \rightleftharpoons \mathrm{NO}_2^{-}(a q)+\mathrm{H}_2 \mathrm{O}(l)\) (b) \(\mathrm{FeBr}_3(s)+\mathrm{Br}^{-}(a q) \rightleftharpoons \mathrm{FeBr}_4{ }^{-}(a q)\) (c) \(\mathrm{Zn}^{2+}(a q)+4 \mathrm{NH}_3(a q) \rightleftharpoons \mathrm{Zn}\left(\mathrm{NH}_3\right)_4{ }^{2+}(a q)\) (d) \(\mathrm{SO}_2(g)+\mathrm{H}_2 \mathrm{O}(l) \rightleftharpoons \mathrm{H}_2 \mathrm{SO}_3(a q)\)

Problem 99E Lewis Acids and Bases (Section) Predict which member of each pair produces the more acidic aqueous solution: (a) K+ or Cu2+,(b) Fe2+ or Fe3+, (c) Al3+or Ga3+.

Problem 100E Lewis Acids and Bases (Section) Which member of each pair produces the more acidic aqueous solution: (a) ZnBr2 or CdCl2,(b) CuCl or Cu(NO3)2, (c) Ca(NO3)2 or NiBr2?

Problem 101AE Triethylamine, (C2H5)3N, has a pKb value of 2.99. Is trimethylamine a stronger base than ammonia, NH3?

Problem 102AE Indicate whether each of the following statements is correct or incorrect. (a) Every Brønsted–Lowry acid is also a Lewis acid. ________________ (b) Every Lewis acid is also a Brønsted–Lowry acid. ________________ (c) Conjugate acids of weak bases produce more acidic solutions than conjugate acids of strong bases. ________________ (d) K+ ion is acidic in water because it causes hydrating water molecules to become more acidic. ________________ (e) The percent ionization of a weak acid in water increases as the concentration of acid decreases.

Use Figure to predict whether the equilibrium lies to the right or to the left in the following reactions: (a) (b)

Problem 104AE The odor of fish is due primarily to amines, especially methylamine (CH3NH2). Fish is often served with a wedge of lemon, which contains citric acid. The amine and the acid react forming a product with no odor, thereby making the less-than-fresh fish more appetizing. Using data from Appendix D, calculate the equilibrium constant for the reaction of citric acid with methylamine, if only the first proton of the citric acid (Ka1) is important in the neutralization reaction.

Problem 105AE Hemoglobin plays a part in a series of equilibria involving protonation-deprotonation and oxygenation-deoxygenation. The overall reaction is approximately as follows HbH+(aq) + O2(aq) ? HbO2(aq) + H+(aq) where Hb stands for hemoglobin and HbO2 for oxyhemoglobin. (a) The concentration of O2 is higher in the lungs and lower in the tissues. What effect does high [O2] have on the position of this equilibrium? (b) The normal pH of blood is 7.4. Is the blood acidic, basic, or neutral? (c) If the blood pH is lowered by the presence of large amounts of acidic metabolism products, a condition known as acidosis results. What effect does lowering blood pH have on the ability of hemoglobin to transport O2?

Problem 106AE Calculate the pH of a solution made by adding 2.50 g of lithium oxide (Li2O) to enough water to make 1.500 L of solution.

Problem 108AE What is the pH of a solution that is 2.5 × 10-9 M in NaOH? Does your answer make sense? What assumption do we normally make that is not valid in this case?

Which of the following solutions has the higher pH? (a) a 0.1 solution of a strong acid or a 0.1solution of a weak acid,(b)a 0.1 solution of an acid with a -3 or one with a 8 -6 , (c) a 0.1 solution of a base with b 4.5 or one with b 6.5.

Problem 109AE Caproic acid (C5H11COOH) is found in small amounts in coconut and palm oils and is used in making artificial flavors. A saturated solution of the acid contains 11 g/L and has a pH of 2.94. Calculate Ka for the acid.

Problem 110AE Butyric acid is responsible for the foul smell of rancid butter. The pKa of butyric acid is 4.84. (a)Calculate the pKb for the butyrate ion. (b) Calculate the pH of a 0.050 M solution of butyric acid. (c) Calculate the pH of a 0.050 M solution of sodium butyrate.

Problem 111AE Arrange the following 0.10 M solutions in order of increasing acidity (decreasing pH): (i) NH4NO3, (ii) NaNO3, (iii) CH3COONH4, (iv) NaF, (v) CH3COONa.

Problem 112AE Many moderately large organic molecules containing basic nitrogen atoms are not very soluble in water as neutral molecules, but they are frequently much more soluble as their acid salts. Assuming that pH in the stomach is 2.5, indicate whether each of the following compounds would be present in the stomach as the neutral base or in the protonated form: nicotine, Kb = 7 × 10-7; caffeine, Kb = 4 × 10-14; strychnine, Kb = 1 × 10-6; quinine, Kb = 1.1 × 10-6.

The amino acid glycine \((H_2N — CH_2 — COOH)\) can participate in the following equilibria in water: \(H_2N — CH_2 — COOH + H_2O \rightleftharpoons H_2N — CH_2 — COO^- + H_3O + K_a = 4.3 \times 10^{-3}\) \(H_2N — CH_2 — COOH + H_2O \rightleftharpoons H_3N — CH_2 — COOH + OH – Kb = 6.0 \times 10^{-5}\) (a) Use the values of \(K_a\) and \(K_b\) to estimate the equilibrium constant for the intramolecular proton transfer to form a zwitterion: \(H_2N — CH_2 — COOH \rightleftharpoons ^{+}H_3N — CH_2 — COO^{–}\) (b) What is the pH of a 0.050 M aqueous solution of glycine? (c) What would be the predominant form of glycine in a solution with pH 13? With pH 1?

The structural formula for acetic acid is shown in Table 16.2.Replacing hydrogen atoms on the carbon with chlorine atoms causes an increase in acidity, as follows: Using Lewis structures as the basis of your discussion, explain the observed trend in acidities in the series. Calculate the pH of a 0.010 M solution of each acid.

Problem 115IE Calculate the number of H+(aq) ions in 1.0 mL of pure water at 25 °C.

How many milliliters of concentrated hydrochloric acid solution (36.0% HCl by mass, density = 1.18 g/mL) are required to produce 10.0 L of a solution that has a pH of 2.05?

Problem 117IE The volume of an adult’s stomach ranges from about 50 mL when empty to 1 L when full. If the stomach volume is 400 mL and its contents have a pH of 2, how many moles of H+ does the stomach contain? Assuming that all the H+ comes from HCl, how many grams of sodium hydrogen carbonate will totally neutralize the stomach acid?

Problem 118IE Atmospheric CO2 levels have risen by nearly 20% over the past 40 years from 315 ppm to 380 ppm. (a) Given that the average pH of clean, unpolluted rain today is 5.4, determine the pH of unpolluted rain 40 years ago. Assume that carbonic acid (H2CO3) formed by the reaction of CO2 and water is the only factor influencing pH. CO2(g) + H2O(l) ? H2CO3(aq) (b) What volume of CO2 at 25 °C and 1.0 atm is dissolved in a 20.0-L bucket of today’s rainwater?

Problem 119IE In many reactions the addition of AlCl3 produces the same effect as the addition of H+. (a) Draw a Lewis structure for AlCl3 in which no atoms carry formal charges, and determine its structure using the VSEPR method. (b) What characteristic is notable about the structure in part (a) that helps us understand the acidic character of AlCl3? (c) Predict the result of the reaction between AlCl3 and NH3 in a solvent that does not participate as a reactant. (d) Which acid–base theory is most suitable for discussing the similarities between AlCl3 and H+?

Problem 120IE What is the boiling point of a 0.10 M solution of NaHSO4 if the solution has a density of 1.002 g/mL?

Use average bond enthalpies from Table 8.4 to estimate the enthalpies of the following gas-phase reactions: Reaction 1: 23+ Reaction 2: - 3+ Are both reactions exothermic? How do these values relate to the different strengths of hydrofluoric and hydrochloric acid?

Cocaine is a weak organic base whose molecular formula is \(\mathrm{C}_{17} \mathrm{H}_{21} \mathrm{NO}_4\). An aqueous solution of cocaine was found to have a pH of 8.53 and an osmotic pressure of 52.7 torr at \(15{ }^{\circ} \mathrm{C}\). Calculate \(K_b\) for cocaine.

Problem 123IE The iodate ion is reduced by sulfite according to the following reaction: IO3–(aq) + 3SO32–(aq) ? I–(aq) + 3 SO42–(aq) The rate of this reaction is found to be first order in IO3–, first order in SO3 2–, and first order in H+. (a) Write the rate law for the reaction. (b) By what factor will the rate of the reaction change if the pH is lowered from 5.00 to 3.50? Does the reaction proceed more quickly or more slowly at the lower pH? (c) By using the concepts discussed in Section, explain how the reaction can be pH-dependent even though H+ does not appear in the overall reaction.

Problem 124IE (a) Using dissociation constants from Appendix D, determine the value for the equilibrium constant for each of the following reactions. (i) HCO3–(aq) + OH-(aq) ? CO32–(aq) + H2O(l) ________________ (ii) NH4+(aq) + CO32–(aq) ? NH3(aq) + HCO3–(aq) (b) We usually use single arrows for reactions when the forward reaction is appreciable (Kmuch greater than 1) or when products escape from the system, so that equilibrium is never established. If we follow this convention, which of these equilibria might be written with a single arrow?