Complete the following acid–base reactions. In each case, indicate whether the equilibrium favors the reactants or the products, and explain your reasoning.
(f) (CH₃)₃C–O^– + H₂O ⇌

Verified step by step guidance

1. Identify the acid and base on both sides of the reaction. In this case, (CH3)3C—O⁻ is the base, and H2O is the acid on the reactant side. On the product side, the conjugate acid of (CH3)3C—O⁻ is (CH3)3C—OH, and the conjugate base of H2O is OH⁻.
2. Determine the relative acid strengths of the acids involved. Compare the pKa values of H2O (as an acid) and (CH3)3C—OH. H2O has a pKa of approximately 15.7, while (CH3)3C—OH has a pKa of approximately 18.
3. Recall that the equilibrium of an acid-base reaction favors the side with the weaker acid and weaker base. Since (CH3)3C—OH has a higher pKa (weaker acid) compared to H2O, the equilibrium will favor the side with (CH3)3C—OH and OH⁻.
4. Write the products of the reaction: (CH3)3C—OH and OH⁻. The reaction can be represented as: (CH3)3C—O⁻ + H2O ⇌ (CH3)3C—OH + OH⁻.
5. Conclude that the equilibrium favors the products because the weaker acid (higher pKa) and weaker base are on the product side. This is consistent with the principle that equilibrium favors the formation of the weaker acid-base pair.

Key Concepts

Acid-Base Theory

Acid-base theory explains the behavior of acids and bases in chemical reactions. According to the Brønsted-Lowry theory, acids are proton donors while bases are proton acceptors. In the given reaction, the tert-butoxide ion ((CH3)3C—O-) acts as a base by accepting a proton from water (H2O), which acts as an acid. Understanding this theory is crucial for predicting the direction of the equilibrium.

Equilibrium Position

The position of equilibrium in a chemical reaction indicates whether the reactants or products are favored. This is determined by the relative strengths of the acids and bases involved. In this case, if the resulting products are weaker acids and bases than the reactants, the equilibrium will favor the products. Conversely, if the reactants are stronger, the equilibrium will favor them.

pKa Values

pKa values are a quantitative measure of the strength of an acid in solution; lower pKa values indicate stronger acids. When analyzing acid-base reactions, comparing the pKa values of the acids and bases involved helps predict the direction of equilibrium. In this reaction, knowing the pKa of water and the conjugate acid formed will help determine whether the equilibrium favors the reactants or products.