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Ch.17 - Additional Aspects of Aqueous Equilibria
Brown - Chemistry: The Central Science 15th Edition
Brown15th EditionChemistry: The Central ScienceISBN: 9780137542970당신이 사용하는 게 아니라요?교과서 변경
모든 교과서Brown 15th EditionCh.17 - Additional Aspects of Aqueous Equilibria문제 86
17장, 문제 86

The acid–base indicator bromcresol green is a weak acid. The yellow acid and blue base forms of the indicator are present in equal concentrations in a solution when the pH is 4.68. What is the pKa for bromcresol green?

검증된 단계별 안내
1
Identify that the problem involves an acid-base indicator, which is a weak acid, and its pKa value needs to be determined.
Recall that when the concentrations of the acid form and the base form of an indicator are equal, the pH of the solution is equal to the pKa of the indicator.
Understand that the given pH value of 4.68 is the point at which the concentrations of the yellow acid form and the blue base form of bromcresol green are equal.
Conclude that the pKa of bromcresol green is equal to the pH at which the concentrations of the two forms are equal, which is 4.68.
Therefore, the pKa for bromcresol green is 4.68.

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주요 개념

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

Acid-Base Indicators

Acid-base indicators are substances that change color in response to changes in pH. They are typically weak acids or bases that exhibit different colors in their protonated and deprotonated forms. For example, bromcresol green appears yellow in acidic conditions and blue in basic conditions, making it useful for determining the pH of a solution.
추천 영상:
가이드 코스
04:30
Acid-Base Indicators

pKa and pH Relationship

The pKa of an acid is the negative logarithm of its acid dissociation constant (Ka) and represents the pH at which the concentrations of the protonated and deprotonated forms of the acid are equal. When the pH of a solution equals the pKa, the acid and its conjugate base are present in equal amounts, which is crucial for understanding the behavior of weak acids and bases in solution.
추천 영상:
가이드 코스
02:09
pH and pOH Calculations

Henderson-Hasselbalch Equation

The Henderson-Hasselbalch equation relates the pH of a solution to the pKa of an acid and the ratio of the concentrations of its deprotonated and protonated forms. It is expressed as pH = pKa + log([A-]/[HA]). This equation is particularly useful for calculating the pKa when the pH and concentrations of the acid and base forms are known, as in the case of bromcresol green.
추천 영상:
가이드 코스
02:40
Henderson-Hasselbalch Equation
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교과서 질문

Rainwater is acidic because CO21g2 dissolves in the water, creating carbonic acid, H2CO3. If the rainwater is too acidic, it will react with limestone and seashells (which are principally made of calcium carbonate, CaCO3). Calculate the concentrations of carbonic acid, bicarbonate ion 1HCO3-2 and carbonate ion 1CO32 - 2 that are in a raindrop that has a pH of 5.60, assuming that the sum of all three species in the raindrop is 1.0 * 10-5 M.

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교과서 질문

Two buffers are prepared by adding an equal number of moles of formic acid (HCOOH) and sodium formate (HCOONa) to enough water to make 1.00 L of solution. Buffer A is prepared using 1.00 mol each of formic acid and sodium formate. Buffer B is prepared by using 0.010 mol of each. (b) Which buffer will have the greater buffer capacity?

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교과서 질문

Which of these equations relates the pOH of a buffer to the p𝐾𝑏 of its weak base, analogous to the Henderson–Hasselbalch equation for weak acids?

a. p𝐾𝑏=pOH+p𝐾𝑏=pOH+log[acid]/[base]

b. p𝐾𝑏=pOH−log[acid]/[base]

c. p𝐾𝑏=pOH−log[base]/[acid]

d. p𝐾𝑏=pOH+log[base]/[[acid]