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Ch. 2 - Acids and Bases: Central to Understanding Organic Chemistry
Bruice - Organic Chemistry 8th Edition
Bruice8th EditionOrganic ChemistryISBN: 9780135213711당신이 사용하는 게 아니라요?교과서 변경
모든 교과서Bruice 8th EditionCh. 2 - Acids and Bases: Central to Understanding Organic Chemistry문제 45c
2장, 문제 45c

At what pH is the concentration of a compound, with a pKa = 4.6, 10 times greater in its basic form than in its acidic form?

검증된 단계별 안내
1
Step 1: Recall the Henderson-Hasselbalch equation, which relates pH, pKa, and the ratio of the concentrations of the basic form ([A⁻]) and acidic form ([HA]) of a compound: pH=pKa+log([A⁻[HA]).
Step 2: Identify the given values in the problem. The pKa of the compound is 4.6, and the ratio of the basic form ([A⁻]) to the acidic form ([HA]) is 10:1. This means [A⁻=10×[HA].
Step 3: Substitute the ratio into the Henderson-Hasselbalch equation. Replace log([A⁻[HA]) with log(10), since the ratio is 10:1.
Step 4: Recall that log(10) equals 1. Substitute this value into the equation: pH=pKa+1.
Step 5: Add the pKa value (4.6) to 1 to determine the pH at which the concentration of the basic form is 10 times greater than the acidic form. The final pH can be calculated using this equation.

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주요 개념

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

pKa and pH Relationship

The pKa value of a compound indicates the pH at which half of the compound is in its acidic form and half is in its basic form. A lower pKa means a stronger acid. The relationship between pKa and pH is crucial for understanding the ionization of weak acids and bases in solution.
추천 영상:
07:45
Identifying pKa values

Henderson-Hasselbalch Equation

The Henderson-Hasselbalch equation relates pH, pKa, and the ratio of the concentrations of the basic and acidic forms of a compound. It is expressed as pH = pKa + log([A-]/[HA]), where [A-] is the concentration of the base and [HA] is the concentration of the acid. This equation is essential for calculating the pH at which specific ratios of acid and base exist.
추천 영상:
05:02
Breaking down the different terms of the Gibbs Free Energy equation.

Concentration Ratios

Understanding concentration ratios is vital for solving the problem. If the concentration of the basic form is 10 times greater than that of the acidic form, this translates to a ratio of [A-]/[HA] = 10. This ratio can be plugged into the Henderson-Hasselbalch equation to find the corresponding pH.
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04:21
How to calculate enantiomeric excess.
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교과서 질문

At what pH is the concentration of a compound, with a pKa = 8.4, 100 times greater in its acidic form than in its basic form? At what pH is 50% of a compound, with a pKa = 7.3, in its basic form?

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교과서 질문

For each of the following compounds, indicate the pH at which

a. 50% of the compound is in a form that possesses a charge.

1. CH3CH2COOH (pKa = 4.9)

2. CH3N+H3 (pKa = 10.7)

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교과서 질문

A naturally occurring amino acid such as alanine has a group that is a carboxylic acid and a group that is a protonated amine. The pKa values of the two groups are shown.

d. Draw the structure of alanine in a solution at pH = 12.

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교과서 질문

A naturally occurring amino acid such as alanine has a group that is a carboxylic acid and a group that is a protonated amine. The pKa values of the two groups are shown.

e. Is there a pH at which alanine is uncharged (that is, neither group has a charge)?

f. At what pH does alanine have no net charge (that is, the amount of negative charge is the same as the amount of positive charge)?

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교과서 질문

Given the data in Problem 47:

a. What pH would you make the water layer to cause the carboxylic acid to dissolve in the water layer and the amine to dissolve in the ether layer?

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교과서 질문

For each of the following compounds, indicate the pH at which

b. more than 99% of the compound is in a form that possesses a charge.

    1. CH3CH2COOH (pKa = 4.9)

    2. CH3N+H3 (pKa = 10.7)

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