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.

Verified step by step guidance

1. Identify the functional groups in each compound: Ethanol (CH3CH2OH) has a hydroxyl group, methylamine (CH3NH2) has an amino group, and acetic acid (CH3COOH) has a carboxylic acid group.
2. Understand the basicity of each functional group: Amines (like methylamine) are generally more basic than alcohols (like ethanol) and carboxylic acids (like acetic acid) because the lone pair on nitrogen is more available for protonation compared to the lone pairs on oxygen.
3. Write the reaction of each compound with a generic acid (HA) to form the conjugate acid: For ethanol, CH3CH2OH + HA → CH3CH2OH2+ + A-. For methylamine, CH3NH2 + HA → CH3NH3+ + A-. For acetic acid, CH3COOH + HA → CH3COOH2+ + A-.
4. Compare the stability of the conjugate acids: The conjugate acid of methylamine (CH3NH3+) is more stable than that of ethanol (CH3CH2OH2+) and acetic acid (CH3COOH2+), making methylamine the most basic.
5. Rank the compounds in decreasing order of basicity: Methylamine > Ethanol > Acetic Acid.

Key Concepts

Amphoteric Compounds

Amphoteric compounds can act as both acids and bases depending on the environment. This dual behavior is crucial in acid-base chemistry, as it allows these substances to participate in various reactions. For example, ethanol can donate a proton (acting as an acid) or accept a proton (acting as a base), depending on the reactants present.

Basicity

Basicity refers to the ability of a substance to accept protons (H+) in a chemical reaction. In the context of the question, the basicity of ethanol, methylamine, and acetic acid can be compared by examining their structures and the stability of their conjugate acids. Methylamine, with its nitrogen atom, is generally more basic than ethanol and acetic acid due to the availability of a lone pair of electrons for protonation.

Conjugate Acids

A conjugate acid is formed when a base accepts a proton. Understanding the formation of conjugate acids is essential for ranking the basicity of the given compounds. For instance, when methylamine reacts with a generic acid (HA), it forms its conjugate acid (CH3NH3+), which can be compared to the conjugate acids of ethanol and acetic acid to determine their relative basicities.