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Ch.17 - Additional Aspects of Aqueous Equilibria
Brown - Chemistry: The Central Science 14th Edition
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Tutti i libri di testoBrown 14th EditionCh.17 - Additional Aspects of Aqueous EquilibriaProblema 32a
Capitolo 17, Problema 32a

You have to prepare a pH = 5.00 buffer, and you have the following 0.10 M solutions available: HCOOH, HCOONa, CH3COOH, CH3COONa, HCN, and NaCN. Which solutions would you use?

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insert step 1> Identify the pKa values of the acids available: HCOOH, CH3COOH, and HCN.
insert step 2> Compare the pKa values to the desired pH of the buffer, which is 5.00.
insert step 3> Choose the acid whose pKa is closest to the desired pH, as this will provide the most effective buffer.
insert step 4> Select the corresponding salt of the chosen acid to pair with it, forming the buffer system.
insert step 5> Use the Henderson-Hasselbalch equation to verify that the chosen acid and its conjugate base can achieve the desired 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, a buffer at pH 5.00 can be created using a weak acid and its salt, which helps maintain the desired pH level.
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03:02
Buffer Solutions

Henderson-Hasselbalch Equation

The Henderson-Hasselbalch equation relates the pH of a buffer solution to the concentration of the acid and its conjugate base. It is expressed as pH = pKa + log([A-]/[HA]), where pKa is the negative logarithm of the acid dissociation constant. This equation is essential for determining the appropriate ratio of acid to base needed to achieve a specific pH.
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Henderson-Hasselbalch Equation

pKa Values

The pKa value is a measure of the strength of an acid in solution, indicating the pH at which half of the acid is dissociated. For effective buffer preparation, it is important to choose a weak acid with a pKa close to the desired pH. In this scenario, knowing the pKa values of the available acids (HCOOH, CH3COOH, HCN) will help identify which acid-base pair can effectively create a buffer at pH 5.00.
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Gas Constant Values
Pratica correlata
Domanda del libro di testo

You have to prepare a pH = 3.50 buffer, and you have the following 0.10 M solutions available: HCOOH, CH3COOH, H3PO4, HCOONa, CH3COONa, and NaH2PO4. How many milliliters of each solution would you use to make approximately 1 L of the buffer?

Domanda del libro di testo

(b) What is the ratio of HCO3- to H2CO3 in an exhausted marathon runner whose blood pH is 7.1?

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Domanda del libro di testo

The accompanying graph shows the titration curves for two monoprotic acids. (d) Estimate the pKa of the weak acid.

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Domanda del libro di testo

You have to prepare a pH = 5.00 buffer, and you have the following 0.10 M solutions available: HCOOH, HCOONa, CH3COOH, CH3COONa, HCN, and NaCN. How many milliliters of each solution would you use to make approximately 1 L of the buffer?

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Domanda del libro di testo

You have to prepare a pH = 3.50 buffer, and you have the following 0.10 M solutions available: HCOOH, CH3COOH, H3PO4, HCOONa, CH3COONa, and NaH2PO4. Which solutions would you use?

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