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Ch.17 - Aqueous Ionic Equilibrium
Tro - Chemistry: A Molecular Approach 4th Edition
Tro4th EditionChemistry: A Molecular ApproachISBN: 9780134112831당신이 사용하는 게 아니라요?교과서 변경
모든 교과서Tro 4th EditionCh.17 - Aqueous Ionic Equilibrium문제 47
17장, 문제 47

A 250.0-mL buffer solution is 0.250 M in acetic acid and 0.250 M in sodium acetate. a. What is the initial pH of this solution? b. What is the pH after the addition of 0.0050 mol of HCl? c. What is the pH after the addition of 0.0050 mol of NaOH?

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1
Identify the components of the buffer solution: acetic acid (CH₃COOH) and sodium acetate (CH₃COONa). Note that acetic acid is a weak acid and sodium acetate is its conjugate base.
Use the Henderson-Hasselbalch equation to find the initial pH of the buffer solution: \( \text{pH} = \text{pK}_a + \log \left( \frac{[\text{A}^-]}{[\text{HA}]} \right) \), where \( \text{pK}_a \) is the negative logarithm of the acid dissociation constant of acetic acid, \( [\text{A}^-] \) is the concentration of acetate ion, and \( [\text{HA}] \) is the concentration of acetic acid.
For part b, calculate the change in moles of acetic acid and acetate ion after adding 0.0050 mol of HCl. HCl will react with the acetate ion to form more acetic acid: \( \text{CH}_3\text{COO}^- + \text{HCl} \rightarrow \text{CH}_3\text{COOH} + \text{Cl}^- \).
Use the Henderson-Hasselbalch equation again to find the new pH after the addition of HCl, using the updated concentrations of acetic acid and acetate ion.
For part c, calculate the change in moles of acetic acid and acetate ion after adding 0.0050 mol of NaOH. NaOH will react with acetic acid to form more acetate ion: \( \text{CH}_3\text{COOH} + \text{NaOH} \rightarrow \text{CH}_3\text{COO}^- + \text{H}_2\text{O} + \text{Na}^+ \). Use the Henderson-Hasselbalch equation to find the new pH after the addition of NaOH.

주요 개념

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

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, or a weak base and its conjugate acid. In this case, the acetic acid and sodium acetate form a buffer that helps maintain a stable pH when HCl or NaOH is added.
추천 영상:
가이드 코스
03:02
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 initial pH of the buffer solution.
추천 영상:
가이드 코스
02:40
Henderson-Hasselbalch Equation

Acid-Base Neutralization

Acid-base neutralization is a chemical reaction where an acid reacts with a base to produce water and a salt, often resulting in a change in pH. In the context of the question, adding HCl (an acid) and NaOH (a base) to the buffer will affect the concentrations of acetic acid and sodium acetate, thus altering the pH. Understanding this concept is crucial for predicting the pH changes after the addition of these substances.
추천 영상:
가이드 코스
05:04
Lewis Acids and Bases
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