An unknown base (B⁻) has been identified as very weak. What does this tell you about the strength of its conjugate acid, HB? Is it stable or unstable? Is it reactive or unreactive?

Name: Organic Chemistry: A Learner Centered Approach
Author: Mullins
ISBN: 9780137566471

Verified step by step guidance

Identify the relationship between the strength of a base and its conjugate acid: A very weak base corresponds to a strong conjugate acid.

Understand the concept of conjugate acid-base pairs: The conjugate acid of a base is formed when the base gains a proton (H⁺).

Consider the stability of the conjugate acid: A strong conjugate acid is typically more stable because it is less likely to donate a proton.

Evaluate the reactivity of the conjugate acid: A strong conjugate acid is generally more reactive in terms of donating a proton compared to a weak acid.

Conclude that the conjugate acid (HB) of a very weak base (B⁻) is strong, stable, and reactive in terms of proton donation.

Key Concepts

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

Conjugate Acid-Base Relationship

In acid-base chemistry, a conjugate acid is formed when a base accepts a proton (H⁺). The strength of a base is inversely related to the strength of its conjugate acid; thus, if a base is very weak, its conjugate acid is likely to be strong. This relationship is fundamental in predicting the behavior of acids and bases in chemical reactions.

Stability of Conjugate Acids

The stability of a conjugate acid is influenced by its ability to stabilize the positive charge that results from protonation. A weak base typically has a conjugate acid that is stable, as it does not readily lose the proton. This stability can be attributed to factors such as electronegativity and resonance, which help distribute the positive charge.

Reactivity of Acids and Bases

The reactivity of an acid or base is often determined by its strength and stability. A weak base, with a stable conjugate acid, tends to be less reactive because it does not easily participate in proton transfer reactions. Conversely, strong acids and bases are more reactive due to their tendency to readily donate or accept protons, respectively.

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Related Practice

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For the following acid–base pairs, (v) show a mechanism for the reaction;

(e)

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Draw the molecular orbital picture of the following molecules and ions. In each, how many electrons are in the p orbital on the central atom? (b) BH₃

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