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Questions and Answers
The stronger the base, the stronger its conjugate acid.
False
Burning fossil fuels is the primary cause of acid rain.
True
Carbon is the most electronegative atom in the second row of the periodic table.
False
Acid rain has no effect on aquatic life.
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CH3COO- is a stronger base than HCOO-.
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NH3 is a stronger base than HO-.
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Marble is resistant to acid rain.
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Heartburn is caused by a lack of stomach acid.
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H2O is a stronger base than CH3OH.
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Methanol behaves as a base when it reacts with methylamine.
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Sodium bicarbonate can neutralize excess hydrochloric acid.
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Carboxylic acids are strong acids.
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An alcohol can only behave as an acid and lose a proton.
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The size of the atom affects the stability of a base more than its electronegativity.
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Amines are typically strong acids.
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Alcohols are stronger acids than carboxylic acids.
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An sp carbon is less electronegative than an sp2 carbon.
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The size of the atom is more important than its electronegativity in determining how well it bears its negative charge when comparing atoms of similar size.
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A protonated amine is more acidic than a protonated alcohol.
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HI is the weakest acid of the hydrogen halides.
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The stronger the acid, the more stable is its conjugate base.
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The electrostatic potential maps show that the strongest base is the most electron-rich.
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The stability of the anions decreases when proceeding down a column in the periodic table.
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The electron density of a halide ion increases as it gets larger in size.
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In a dilute aqueous solution, the concentration of water is approximately 50M.
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Ka values are often expressed in place of pKa values in acid-base reactions.
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A strong acid will have a high pKa value.
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The pH scale is used to describe the tendency of a compound to lose its proton.
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Coffee is more acidic than lemon juice.
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Rain is basic with a pH value of 5.5.
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Sulfuric acid is a weak acid with a pKa value of 6.4.
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PKa is equal to -log [H+].
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Electron delocalization decreases the acidity of the conjugate acid of a carboxylic acid.
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When a carboxylic acid loses a proton, the negative charge resides on its single oxygen atom.
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All Brønsted-Lowry acids are also Lewis acids.
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Borane (BH3) is a base because it has a lone pair of electrons.
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A nucleophile is a compound that shares its lone pair with a proton.
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Ammonia is a base in the reaction with a proton and a nucleophile in the reaction with a carbon atom.
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Inductive electron withdrawal by oxygen decreases the electron density of the positively charged oxygen.
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The term base is used to refer to compounds that share their lone pair with a proton or with an atom other than a proton.
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Study Notes
Acidity and Basicity
- In a dilute aqueous solution, the concentration of water is fairly constant (55.5M) and can be removed from the expression, giving rise to the term Ka, which measures the strength of an acid.
- The value of Ka ranges from 10^10 for very strong acids to 10^(-50) for very weak acids.
- To deal with these large and small numbers, chemists often express pKa values, which range from -10 to 50.
- A strong acid has a low pKa value, while a weak acid has a high pKa value.
pH and pKa
- pH measures the concentration of protons in a solution, ranging from 0 to 14.
- pKa indicates the tendency of a compound to lose its proton, and is characteristic of a particular compound, like a melting point or boiling point.
- pH and pKa are not the same, and should not be confused.
Acid-Base Reactions
- Acid rain is formed when water reacts with sulfur dioxide and nitrogen oxides, producing strong acids like sulfuric acid and nitric acid.
- Acid rain has many deleterious effects, such as destroying aquatic life, making soil acidic, and causing the deterioration of building materials.
Organic Acids and Bases
- Carboxylic acids (e.g., acetic acid, formic acid) have pKa values ranging from 3 to 5, making them weak acids.
- Alcohols (e.g., methyl alcohol, ethyl alcohol) have pKa values close to 16, making them even weaker acids.
- Amines and ammonia have high pKa values, making them strong bases.
Factors Affecting pKa Value
- The stability of a base is affected by its electronegativity and size.
- Within a row of the periodic table, the more electronegative atom will have a stronger acid, and a more stable (weaker) conjugate base.
- Hybridization affects the acidity of a hydrogen atom bonded to it, with sp hybridization being more electronegative than sp2, and sp2 more electronegative than sp3.
Lewis Acids and Bases
- A Lewis acid is a species that accepts a share in an electron pair, and includes all proton-donating compounds and some additional compounds that do not have protons.
- A Lewis base is a species that donates a share in an electron pair, and includes all compounds that share their lone pair with a proton or an atom such as boron, aluminum, or carbon.
- The term nucleophile is used for a compound that shares its lone pair with an atom other than a proton.
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Description
Learn about acid-base reactions in dilute aqueous solutions, Ka values, and how they measure acid strength. Understand how pKa values are used to simplify very small or large Ka values.
