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Ch.17 - Additional Aspects of Aqueous Equilibria
Brown - Chemistry: The Central Science 14th Edition
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoBrown 14th EditionCh.17 - Additional Aspects of Aqueous EquilibriaProblema 21a
Capitolo 17, Problema 21a

(a) Calculate the pH of a buffer that is 0.12 M in lactic acid and 0.11 M in sodium lactate.

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Identify the acid and its conjugate base in the buffer system. Here, lactic acid (HC3H5O3) is the weak acid and sodium lactate (NaC3H5O3) is the salt of its conjugate base (C3H5O3-).
Write the acid dissociation reaction for lactic acid: HC3H5O3(aq) ⇌ H+(aq) + C3H5O3-(aq).
Use the Henderson-Hasselbalch equation to calculate the pH of the buffer: pH = pKa + \(\log\)\(\left\)(\(\frac{[\text{Conjugate Base}\)]}{[\(\text{Acid}\)]}\(\right\)).
Find the pKa value of lactic acid from a reliable source, such as a chemistry textbook or database.
Substitute the concentrations of the acid ([HC3H5O3] = 0.12 M) and the conjugate base ([C3H5O3-] = 0.11 M), along with the pKa value, into the Henderson-Hasselbalch equation to solve for pH.

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Buffer Solutions

Buffer solutions are mixtures that resist changes in pH when small amounts of acid or base are added. They typically consist of a weak acid and its conjugate base, or a weak base and its conjugate acid. In this case, lactic acid (weak acid) and sodium lactate (conjugate base) form a buffer system that helps maintain a stable pH.
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Buffer Solutions

Henderson-Hasselbalch Equation

The Henderson-Hasselbalch equation is a mathematical formula used to calculate the pH of a buffer solution. It is expressed as pH = pKa + log([A-]/[HA]), where pKa is the negative logarithm of the acid dissociation constant, [A-] is the concentration of the conjugate base, and [HA] is the concentration of the weak acid. This equation is essential for determining the pH of the given buffer solution.
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Henderson-Hasselbalch Equation

pKa and Acid-Base Equilibrium

pKa is a measure of the strength of an acid in solution, representing the pH at which half of the acid is dissociated. It is crucial for understanding acid-base equilibria, as it helps predict how a buffer will respond to changes in pH. For lactic acid, knowing its pKa allows for accurate calculations of the buffer's pH using the Henderson-Hasselbalch equation.
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Acid-Base Indicators
Pratica correlata
Domanda del libro di testo

(b) Calculate the pH of a buffer formed by mixing 85 mL of 0.13 M lactic acid with 95 mL of 0.15 M sodium lactate.

Domanda del libro di testo

(b) Calculate the percent ionization of 0.125 M lactic acid in a solution containing 0.0075 M sodium lactate.

Domanda del libro di testo

Which of the following solutions is a buffer? (a) A solution made by mixing 100 mL of 0.100 M CH3COOH and 50 mL of 0.100 M NaOH, (b) a solution made by mixing 100 mL of 0.100 M CH3COOH and 500 mL of 0.100 M NaOH, (c) A solution made by mixing 100 mL of 0.100 M CH3COOH and 50 mL of 0.100 M HCl, (d) A solution made by mixing 100 mL of 0.100 M CH3COOK and 50 mL of 0.100 M KCl.

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