Skip to main content
Ch.16 - Acid-Base Equilibria
Brown - Chemistry: The Central Science 15th Edition
Brown15th EditionChemistry: The Central ScienceISBN: 9780137542970Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoBrown 15th EditionCh.16 - Acid-Base EquilibriaProblema 75
Capitolo 16, Problema 75

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.

Guida verificata passo dopo passo
1
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-].

Concetti chiave

Ecco i concetti essenziali che devi comprendere per rispondere correttamente alla domanda.

Base Ionization and Kb

Ethylamine (C2H5NH2) is a weak base that partially ionizes in water to produce hydroxide ions (OH-) and its conjugate acid (C2H5NH3+). The base dissociation constant (Kb) quantifies the extent of this ionization, with a higher Kb indicating a stronger base. In this case, Kb = 6.4 x 10^-4 helps determine the concentration of OH- produced in the solution.
Video consigliato:
Percorso guidato
03:50
Characteristics of Ka and Kb

Equilibrium Concentrations

To find the concentration of OH- in the solution, we set up an equilibrium expression based on the ionization of ethylamine. Using an ICE (Initial, Change, Equilibrium) table, we can express the changes in concentrations of the reactants and products at equilibrium. This allows us to solve for the concentration of OH- using the Kb value.
Video consigliato:
Percorso guidato
02:35
Thermal Equilibrium

pH and pOH Calculations

The pH of a solution is a measure of its acidity, while pOH measures its basicity. They are related through the equation pH + pOH = 14. Once the concentration of OH- is determined, the pOH can be calculated using the formula pOH = -log[OH-]. Subsequently, the pH can be found by rearranging the equation to pH = 14 - pOH.
Video consigliato:
Percorso guidato
02:09
pH and pOH Calculations
Pratica correlata
Domanda del libro di testo

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

752
views
Domanda del libro di testo

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-?

1229
views
Domanda del libro di testo

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.

462
views
Domanda del libro di testo

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

512
views