Open Question
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^-
Ch.16 - Acid-Base Equilibria
Chapter 16, Problem 71
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.
Verified step by step guidance1
Identify the reaction: Ethylamine (C2H5NH2) is a weak base and will react with water to form C2H5NH3+ and OH-. Write the equilibrium expression for this reaction.
Write the expression for the base dissociation constant (Kb): Kb = [C2H5NH3+][OH-] / [C2H5NH2].
Set up an ICE (Initial, Change, Equilibrium) table to determine the concentrations of the species at equilibrium. Assume the initial concentration of OH- and C2H5NH3+ is 0, and the change in concentration for C2H5NH2 is -x, for OH- and C2H5NH3+ is +x.
Substitute the equilibrium concentrations from the ICE table into the Kb expression: Kb = (x)(x) / (0.075 - x).
Solve for x, which represents the concentration of OH- at equilibrium. Use the approximation method if x is small compared to the initial concentration, then calculate the pH using the relation pH = 14 - pOH, where pOH = -log[OH-].
Related Practice
Textbook Question
Write the chemical equation and the Kb expression for the reaction of each of the following bases with water: (a) propylamine, C3H7NH2
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Textbook Question
Write the chemical equation and the Kb expression for the reaction of each of the following bases with water: (c) benzoate ion, C6H5CO2-
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Open Question
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?
Textbook Question
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-?
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Textbook Question
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.
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