Using qualitative reasoning for the acid–base reactions shown,
(i) which is stronger, the base or the conjugate base?
(ii) Which side of the reaction is favored?
(iii) Would you expect a K_eq greater than or less than 1?
(a)

Verified step by step guidance

Step 1: Identify the acid and base on the reactant side of the reaction. Recall that the acid donates a proton (H⁺), and the base accepts a proton.

Step 2: Determine the conjugate acid and conjugate base on the product side. The conjugate acid is formed when the base gains a proton, and the conjugate base is formed when the acid loses a proton.

Step 3: Compare the relative strengths of the base and the conjugate base. Use the pKa values of the acids (the acid and the conjugate acid) to infer the relative strengths of their conjugate bases. A lower pKa indicates a stronger acid, and its conjugate base will be weaker.

Step 4: Determine which side of the reaction is favored. Acid–base reactions favor the side with the weaker acid and weaker base. Use the pKa values to identify the weaker acid and base.

Step 5: Predict whether the equilibrium constant (K_eq) is greater than or less than 1. If the reaction favors the products, K_eq > 1. If the reaction favors the reactants, K_eq < 1.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.

Video duration:

Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Acid-Base Strength

Acid-base strength is determined by the ability of an acid to donate protons (H+) and a base to accept protons. Strong acids completely dissociate in solution, while weak acids only partially dissociate. The strength of a conjugate base is inversely related to the strength of its corresponding acid; a strong acid has a weak conjugate base, and vice versa.

Equilibrium and Reaction Favorability

In acid-base reactions, the position of equilibrium indicates which side is favored. The side with the weaker acid and weaker base is favored because it represents a more stable state. This is often assessed using the relative strengths of the acids and bases involved, where the equilibrium will shift towards the formation of the weaker acid and base.

Equilibrium Constant (K)

The equilibrium constant (K) quantifies the ratio of the concentrations of products to reactants at equilibrium. For acid-base reactions, if K is greater than 1, the products are favored, indicating a stronger base or acid on that side. Conversely, if K is less than 1, the reactants are favored, suggesting a weaker base or acid is present.

Recommended video:

Guided course