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Ch.17 - Applications of Aqueous Equilibria
McMurry - Chemistry 8th Edition
McMurry8th EditionChemistryISBN: 9781292336145당신이 사용하는 게 아니라요?교과서 변경
모든 교과서McMurry 8th EditionCh.17 - Applications of Aqueous Equilibria문제 72
17장, 문제 72

A food chemist studying the formation of lactic acid in sour milk prepares a buffer that is 0.58 M in lactic acid (HC3H5O3) and 0.36 M in sodium lactate (NaC3H5O3). Use the Henderson–Hasselbalch equation to calculate the pH of the buffer solution.

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1
Identify the components of the buffer solution: lactic acid (HC3H5O3) as the weak acid and sodium lactate (NaC3H5O3) as the conjugate base.
Write the Henderson–Hasselbalch equation: \( \text{pH} = \text{pK}_a + \log \left( \frac{[\text{A}^-]}{[\text{HA}]} \right) \), where \([\text{A}^-]\) is the concentration of the conjugate base and \([\text{HA}]\) is the concentration of the weak acid.
Look up or calculate the \(\text{pK}_a\) of lactic acid. The \(\text{pK}_a\) is the negative logarithm of the acid dissociation constant \(K_a\).
Substitute the given concentrations into the Henderson–Hasselbalch equation: \([\text{A}^-] = 0.36\, \text{M}\) and \([\text{HA}] = 0.58\, \text{M}\).
Calculate the pH by solving the Henderson–Hasselbalch equation with the substituted values.

주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Henderson-Hasselbalch Equation

The Henderson-Hasselbalch equation is a mathematical formula used to calculate the pH of a buffer solution. It relates the pH of the solution to the pKa of the weak acid and the ratio of the concentrations of the conjugate base to the weak acid. The equation is expressed as pH = pKa + log([A-]/[HA]), where [A-] is the concentration of the conjugate base and [HA] is the concentration of the weak acid.
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가이드 코스
02:40
Henderson-Hasselbalch Equation

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 and sodium lactate form a buffer system that helps maintain a stable pH in the solution, which is crucial for many biochemical processes.
추천 영상:
가이드 코스
03:02
Buffer Solutions

pKa and Acid-Base Equilibrium

The pKa is a measure of the strength of an acid in solution, defined as the negative logarithm of the acid dissociation constant (Ka). It indicates the pH at which half of the acid is dissociated into its conjugate base. Understanding pKa is essential for using the Henderson-Hasselbalch equation, as it helps determine the pH of the buffer solution based on the concentrations of the acid and its conjugate base.
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가이드 코스
04:30
Acid-Base Indicators
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