Textbook Question
Calculate the pH of the following solutions.
a. 5.00 g of HBr in 100 mL of aqueous solution
b. 1.50 g of NaOH in 50 mL of aqueous solution
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Ch. 2 - Acids and Bases; Functional Groups
Wade9th EditionOrganic ChemistryISBN: 9780135213728
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Table of contents
- Ch.1 - Structure and Bonding107
- Ch. 2 - Acids and Bases; Functional Groups115
- Ch.3 - Structure and Stereochemistry of Alkanes100
- Ch.4 - The Study of Chemical Reactions99
- Ch.5 - Stereochemistry93
- Ch.6 - Alkyl Halides; Nucleophilic Substitution118
- Ch. 7 - Structure and Synthesis of Alkenes; Elimination158
- Ch.8 - Reactions of Alkenes171
- Ch.9 - Alkynes91
- Ch.10 - Structure and Synthesis of Alcohols143
- Ch.11 - Reactions of Alcohols104
- Ch. 12 - Infrared Spectroscopy and Mass Spectrometry22
- Ch. 13 - Nuclear Magnetic Resonance Spectroscopy45
- Ch. 14 - Ethers, Epoxides, and Thioethers72
- Ch. 15 - Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy89
- Ch. 16 - Aromatic Compounds74
- Ch. 17 - Reactions of Aromatic Compounds126
- Ch. 18 - Ketones and Aldehydes193
- Ch. 19 - Amines129
- Ch. 20 - Carboxylic Acids77
- Ch. 21 - Carboxylic Acid Derivatives141
- Ch. 22 - Condensations and Alpha Substitutions of Carbonyl Compounds175
- Ch. 23 - Carbohydrates and Nucleic Acids93
- Ch. 24 - Amino Acids, Peptides, and Proteins54
Chapter 2, Problem 9d
Ammonia appears in [TABLE 2-2] as both an acid and a conjugate base.
d. Show how methanol (CH3OH) can serve as both an acid and a base. Write an equation for the reaction of methanol with sulfuric acid.
Verified step by step guidance1
Methanol (CH₃OH) can act as an acid by donating a proton (H⁺) to a base. When methanol donates a proton, it forms the methoxide ion (CH₃O⁻). This is an example of methanol acting as an acid.
Methanol can also act as a base by accepting a proton from an acid. When methanol accepts a proton, it forms the methanol cation (CH₃OH₂⁺). This is an example of methanol acting as a base.
To show methanol acting as an acid, consider its reaction with a strong base like sodium hydroxide (NaOH). The equation would be: CH₃OH + NaOH → CH₃O⁻ + Na⁺ + H₂O.
To show methanol acting as a base, consider its reaction with a strong acid like sulfuric acid (H₂SO₄). The equation would be: CH₃OH + H₂SO₄ → CH₃OH₂⁺ + HSO₄⁻.
In the reaction with sulfuric acid, methanol accepts a proton from sulfuric acid, demonstrating its ability to act as a base. This reaction highlights the dual nature of methanol as both an acid and a base.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Acid-Base Duality
Acid-base duality refers to the ability of certain substances to act as both an acid and a base, depending on the reaction context. Methanol (CH3OH) can donate a proton, acting as an acid, or accept a proton, acting as a base. This dual behavior is crucial for understanding methanol's role in chemical reactions, such as its interaction with sulfuric acid.
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The Lewis definition of acids and bases.
Conjugate Acid-Base Pairs
Conjugate acid-base pairs are two species that transform into each other by the gain or loss of a proton. In the table, ammonia (NH3) and ammonium ion (NH4+) are an example, where NH3 acts as a base and NH4+ as its conjugate acid. Understanding these pairs helps in predicting the direction of acid-base reactions and the relative strength of acids and bases.
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pKa and Acid Strength
The pKa value is a measure of the acidity of a substance, indicating how easily it donates a proton. Lower pKa values correspond to stronger acids. In the table, methanol has a pKa of 15.9, indicating it is a very weak acid compared to sulfuric acid, which is a strong acid. This concept is essential for predicting the behavior of methanol in acid-base reactions.
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Related Practice
Textbook Question
Ammonia appears in [TABLE 2-2 ] as both an acid and a conjugate base. a. Explain how ammonia can act as both an acid and a base. Which of these roles does it commonly fill in aqueous solutions?
b. Show how water can serve as both an acid and a base.
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Textbook Question
Ethanol, methylamine, and acetic acid are all amphoteric, reacting as either acids or bases depending on the conditions.
a. Rank ethanol, methylamine, and acetic acid in decreasing order of acidity. In each case, show the equation for the reaction with a generic base (B:−) to give the conjugate base.
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Textbook Question
Circle the member of each pair that is more soluble in water.
a. CH3CH2OCH2CH3 or CH3CH2CH2CH2CH3
b. CH3CH2OCH2CH3 or CH3CH2CH2OH
c. CH3CH2NHCH3 or CH3CH2CH2CH3
d. CH3CH2OH or CH3CH2CH2CH2OH
e.
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Textbook Question
Ethanol, methylamine, and acetic acid are all amphoteric, reacting as either acids or bases depending on the conditions.
b. Rank ethanol, methylamine, and acetic acid in decreasing order of basicity. In each case, show the equation for the reaction with a generic acid (HA) to give the conjugate acid.
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Textbook Question
Write equations for the following acid–base reactions. Use the information in Table 2-2 or Appendix 4 to predict whether the equilibrium will favor the reactants or the products.
a. HCOOH + –CN
b. CH3COO– + CH3OH
c. (CH3)2CHOH + NaNH2
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