17. Acid and Base Equilibrium

Acid/Base Dissociation Constant

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16.5 pH Calculations for Weak Acids and Bases | General Chemistry

Chad's Prep

170

Practice this topic

If the Kb of NH₃ is 1.76 x 10^-5, determine the acid dissociation constant of its conjugate acid.

Which Bronsted-Lowry base has the greatest concentration of hydroxide ions?

532

Which Bronsted-Lowry acid has the weakest conjugate base?

The K_a value for a weak acid is _________ than the K_a value for a strong acid because the weak acid ionizes to a _________ extent than the strong acid.

244

Calculate the pH of a 0.500 M pyridine (C₅H₅N) solution. K_b value for pyridine is 1.7 × 10⁻⁹.

777

Determine the pH of 0.450 M HC₇H₅O₂. The K_a for HC₇H₅O₂ is 6.5 × 10⁻⁵.

302

What is the pH of a 0.250 M NH₄Cl solution? K_b for NH₃ = 1.8 × 10⁻⁵.

165

Hypobromous acid (K_a = 2.8 × 10⁻⁹) and hydrocyanic acid (K_a = 4.9 × 10⁻¹⁰) are both weak acids. Determine if reactants or products are favored in the following reaction.

HBrO (aq) + CN⁻ (aq) ⇌ BrO⁻ (aq) + HCN (aq)

a) reactants b) products c) both directions are favored equally d) neither direction is favored

142

Identify a Bronsted-Lowry acid with weakest conjugate base.

a) H₃BO₃ K_a = 5.4 × 10⁻¹⁰

b) HF K_a = 3.5 × 10⁻⁴

c) HNO₂ K_a = 4.6 × 10⁻⁴

d) HClO K_a = 2.9 × 10⁻⁸

110

Identify which of the compounds is the strongest species.

a) Iodic acid pK_a = 0.80 b) Acetic acid pK_b = 9.24 c) Formic acid pK_a = 3.75 d) Ammonium pK_b = 4.75

105

Determine the pK_a given the Kb of the following bases:

i) NH₃ K_b = 1.76 × 10⁻⁵ ; NH₄⁺ pK_a = ____________

ii) C₆H₅NH₂ K_b = 3.9 × 10⁻¹⁰; C₆H₅NH₃⁺ pK_a = ____________

105

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+.(b) Which acid would have the smallest aciddissociation constant, Ka?

340

Classify each acid as strong or weak. If the acid is weak, write an expression for the acid ionization constant (Ka). d. H2CO3

447

The following pictures represent solutions of three salts NaA (A- = X-, Y-, or Z-); water molecules and Na+ ions have been omitted for clarity.

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The following picture represents the hydrated metal cation M1H2O26 n + , where n = 1, 2, or 3.

(a) Write a balanced equation for the reaction of M1H2O26 n + with water and write the equilibrium equation for the reaction.

131

The following picture represents the hydrated metal cation M1H2O26 n + , where n = 1, 2, or 3.

(b) Does the equilibrium constant increase, decrease, or remain the same as the value of n increases? Explain.

174

Rank the solutions in order of decreasing [H3O+]: 0.10 M HCl; 0.10 M HF; 0.10 M HClO; 0.10 M HC6H5O.

2331

Pick the stronger base from each pair. c. F- or ClO-

1700

comments

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+1aq2 as a product and then with the hydronium ion: (a) C6H5COOH

630

Choose from the conjugate acid–base pairs HSO4- >SO42-, HF>F-, and NH4+>NH3 to complete the following equation with the pair that gives an equilibrium constant Kc 7 1. _____ + NO2 - S _____ + HNO2

506

The hypochlorite ion, ClO-, acts as a weak base. (a) Is ClO- a stronger or weaker base than hydroxylamine?

1643

Write the chemical equation and the Kb expression for the reaction of each of the following bases with water: (c) benzoate ion, C6H5CO2-

335

Write the chemical equation and the Kb expression for the reaction of each of the following bases with water: (a) propylamine, C3H7NH2

529

Use the acid-dissociation constants in Table 16.3 to arrange these oxyanions from strongest base to weakest: SO42-, CO32-, SO32-, and PO43-.

1191

Which is the stronger base, the acetate ion or the hypochlorite ion?

364

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?

1101

Calculate Kb values for CH3COO- and ClO-.

1358

Given that Kb for ammonia is 1.8 * 10-5 and that for hydroxylamine is 1.1 * 10-8, which is the stronger base?

868

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.

420

The Kb for methylamine 1CH3NH22 at 25 °C is given in Appendix D. (a) Write the chemical equation for the equilibrium that corresponds to Kb.

427

Write equations showing how each weak base ionizes water to form OH-. Also write the corresponding expression for Kb. c. C2H5NH2

698

Write equations showing how each weak base ionizes water to form OH-. Also write the corresponding expression for Kb. b. C6H5NH2

190

Write equations showing how each weak base ionizes water to form OH-. Also write the corresponding expression for Kb. a. CO32-

721

Look up the values of Ka in Appendix C for C6H5OH, HNO3, CH3CO2H, and HOCl, and arrange these acids in order of: (b) Decreasing percent dissociation.

414

Salts containing the phosphate ion are added to municipal water supplies to prevent the corrosion of lead pipes. (a) Based on the pKa values for phosphoric acid 1pKa1 = 7.5 * 10 - 3, pKa2 = 6.2 * 10 - 8, pKa3 = 4.2 * 10 - 132 what is the Kb value for the PO43 - ion?

247

Which, if any, of the following statements are true? (a) The stronger the base, the smaller the pKb. (b) The stronger the base, the larger the pKb. (c) The stronger the base, the smaller the Kb. (d) The stronger the base, the larger the Kb. (e) The stronger the base, the smaller the pKa of its conjugate acid. (f) The stronger the base, the larger the pKa of its conjugate acid.

1507

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.

934

Write a balanced net ionic equation and the corresponding equilibrium equation for the reaction of the following weak bases with water. (c) Cyanide ion, CN

222

The amino acid glycine 1H2N¬CH2¬COOH2 can participate in the following equilibria in water: H2N¬CH2¬COOH + H2OΔ H2N¬CH2¬COO- + H3O+ Ka = 4.3 * 10-3 H2N¬CH2¬COOH + H2OΔ+H3N¬CH2¬COOH + OH- Kb = 6.0 * 10-5 (a) Use the values of Ka and Kb to estimate the equilibrium constant for the intramolecular proton transfer to form a zwitterion: H2N¬CH2¬COOH Δ +H3N¬CH2¬COO-

663

Using values of Kb in Appendix C, calculate values of Ka for each of the following ions. (a) Propylammonium ion, C3H7NH3+

606

Using values of Ka in Appendix C, calculate values of Kb for each of the following ions. (a) Fluoride ion, F-

431

Nicotine 1C10H14N22 can accept two protons because it has two basic N atoms 1Kb1 = 1.0 * 10-6; Kb2 = 1.3 * 10-112. Calculate the values of Ka for the conjugate acids C10H14N2H+ and C10H14N2H22 + .

304

Using dissociation constants from Appendix D, determine the value for the equilibrium constant for each of the following reactions. (i) HCO3-1aq2 + OH-1aq2 ΔCO32-1aq2 + H2O1l2 (ii) NH4+1aq2 + CO32-1aq2 ΔNH31aq2 + HCO3-1aq2

660

What is the 𝐾a reaction of hcn?

Open Question

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