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Ch.17 - Additional Aspects of Aqueous Equilibria
Brown - Chemistry: The Central Science 14th Edition
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232Not the one you use?Change textbook
All textbooksBrown 14th EditionCh.17 - Additional Aspects of Aqueous EquilibriaProblem 4a
Chapter 17, Problem 4a

The following diagram represents a buffer composed of equal concentrations of a weak acid, HA, and its conjugate base, A-. The heights of the columns are proportional to the concentrations of the components of the buffer. (a) Which of the three drawings, (1), (2), or (3), represents the buffer after the addition of a strong acid? [Section 17.2]

Verified step by step guidance
1
Identify the components of the buffer: a weak acid (HA) and its conjugate base (A-).
Understand that adding a strong acid to the buffer will increase the concentration of H+ ions.
Recognize that the added H+ ions will react with the conjugate base (A-) to form more of the weak acid (HA).
Determine that the concentration of the conjugate base (A-) will decrease, while the concentration of the weak acid (HA) will increase.
Look for the drawing where the column representing HA is taller and the column representing A- is shorter compared to the original buffer.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Buffer Solutions

A buffer solution is a system that resists changes in pH upon the addition of small amounts of acid or base. It typically consists of a weak acid and its conjugate base in equilibrium. This equilibrium allows the buffer to neutralize added acids or bases, maintaining a relatively stable pH.
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Buffer Solutions

Weak Acids and Conjugate Bases

Weak acids partially dissociate in solution, establishing an equilibrium between the undissociated acid (HA) and its ions (H+ and A-). The conjugate base (A-) can react with added H+ ions from a strong acid, minimizing the change in pH. Understanding this equilibrium is crucial for predicting how a buffer will respond to external changes.

Effect of Strong Acid on Buffer

When a strong acid is added to a buffer solution, it increases the concentration of H+ ions. The weak acid component of the buffer will react with these H+ ions, shifting the equilibrium and converting some of the conjugate base (A-) into more weak acid (HA). This process helps to mitigate the pH change, but the buffer's capacity is limited and can be overwhelmed if too much strong acid is added.
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Effective Buffer Range
Related Practice
Textbook Question

The following diagram represents a buffer composed of equal concentrations of a weak acid, HA, and its conjugate base, A-. The heights of the columns are proportional to the concentrations of the components of the buffer. (c) Which of the three represents a situation that cannot arise from the addition of either an acid or a base? [Section 17.2]

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Textbook Question

The following figure represents solutions at various stages of the titration of a weak acid, HA, with NaOH. (The Na+ ions and water molecules have been omitted for clarity.) To which of the following regions of the titration curve does each drawing correspond: (b) after addition of NaOH but before the equivalence point? [Section 17.3]

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Textbook Question

The beaker on the right contains 0.1 M acetic acid solution with methyl orange as an indicator. The beaker on the left contains a mixture of 0.1 M acetic acid and 0.1 M sodium acetate with methyl orange. (a) Using Figures 16.8 and 16.9, which solution has a higher pH?

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Textbook Question

The beaker on the right contains 0.1 M acetic acid solution with methyl orange as an indicator. The beaker on the left contains a mixture of 0.1 M acetic acid and 0.1 M sodium acetate with methyl orange. (b) Which solution is better able to maintain its pH when small amounts of NaOH are added? Explain. [Sections 17.1 and 17.2]

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