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Ch.17 - Additional Aspects of Aqueous Equilibria
Brown - Chemistry: The Central Science 14th Edition
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232당신이 사용하는 게 아니라요?교과서 변경
모든 교과서Brown 14th EditionCh.17 - Additional Aspects of Aqueous Equilibria문제 26a
17장, 문제 26a

You are asked to prepare a pH = 4.00 buffer starting from 1.50 L of 0.0200 M solution of benzoic acid 1C6H5COOH2 and any amount you need of sodium benzoate 1C6H5COONa2. (a) What is the pH of the benzoic acid solution prior to adding sodium benzoate?

검증된 단계별 안내
1
Identify the chemical species involved: benzoic acid (C6H5COOH) is a weak acid, and its dissociation in water can be represented as C6H5COOH ⇌ C6H5COO⁻ + H⁺.
Use the expression for the acid dissociation constant (Ka) for benzoic acid: Ka = [C6H5COO⁻][H⁺] / [C6H5COOH].
Look up the Ka value for benzoic acid, which is typically around 6.3 x 10⁻⁵.
Assume that the initial concentration of benzoic acid is 0.0200 M and that the change in concentration due to dissociation is small compared to the initial concentration.
Set up an ICE (Initial, Change, Equilibrium) table to solve for the concentration of H⁺ ions at equilibrium, and then calculate the pH using the formula pH = -log[H⁺].

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주요 개념

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pH and pKa

pH is a measure of the acidity or basicity of a solution, defined as the negative logarithm of the hydrogen ion concentration. The pKa is the negative logarithm of the acid dissociation constant (Ka) and indicates the strength of an acid. For weak acids like benzoic acid, the pH can be calculated using the formula pH = pKa + log([A-]/[HA]), where [A-] is the concentration of the conjugate base and [HA] is the concentration of the acid.
추천 영상:
가이드 코스
02:33
The pH Scale

Benzoic Acid as a Weak Acid

Benzoic acid (C6H5COOH) is a weak acid that partially dissociates in solution. Its dissociation can be represented by the equation C6H5COOH ⇌ C6H5COO- + H+. The extent of this dissociation is characterized by its Ka value, which is relatively low, indicating that at equilibrium, the concentration of undissociated benzoic acid remains significant compared to its dissociated ions.
추천 영상:
가이드 코스
00:44
ICE Charts of Weak Acids

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, which can neutralize added acids or bases. In this case, the benzoic acid and sodium benzoate will form a buffer system, allowing the solution to maintain a stable pH when sodium benzoate is added.
추천 영상:
가이드 코스
03:02
Buffer Solutions
관련 실천
교과서 질문

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교과서 질문

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교과서 질문

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교과서 질문

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