17. Acid and Base Equilibrium

Acid/Base Dissociation Constant

07:50

The Science Classroom

16.5 pH Calculations for Weak Acids and Bases | General Chemistry

Chad's Prep

213

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?

594

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.

316

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

983

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

382

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

238

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

233

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

165

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

157

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 = ____________

162

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?

452

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

518

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

210

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.

188

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.

235

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

2538

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

1862

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

771

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

598

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

1838

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

407

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

643

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

1353

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

423

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?

1211

Calculate Kb values for CH3COO- and ClO-.

1558

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

1003

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.

500

The value of Ka for nitrous acid 1HNO22 at 25 °C is given in Appendix D. (a) Write the chemical equation for the equilibrium that corresponds to Ka.

493

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.

519

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

800

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

276

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

832

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.

520

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?

311

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.

1670

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.

1051

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

300

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-

782

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

720

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

540

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 + .

385

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

768

What is the 𝐾a reaction of hcn?

150

What is K_b for the conjugate base of HCN (K_a = 4.9 × 10^-10)?

What is K_b for the conjugate base of HCN (K_a = 4.9 × 10⁻¹⁰)?

Given that K_a for HIO is 3.2×10⁻¹¹ at 25 °C, what is the value of 𝐾_b for IO⁻ at 25 °C?

Given that a base has a K_b value of 8.36×10⁻⁴, what is the K_a of its conjugate acid?