Question

Designate the Bronsted-Lowry acid and the BronstedLowry base on the left side of each equation, and also designate the conjugate acid and conjugate base on the right side. (a) \(\mathrm{HBrO}(a q)+\mathrm{H}_{2} \mathrm{O}(I) \rightleftharpoons \mathrm{H}_{3} \mathrm{O}^{+}(a q)+\mathrm{BrO}^{-}(a q)\) (b) \(\mathrm{HSO}_{4}^{-}(a q)+\mathrm{HCO}_{3}^{-}(a q) \rightleftharpoons\) \(\mathrm{SO}_{4}^{2-}(a q)+\mathrm{H}_{2} \mathrm{CO}_{3}(a q)\) (c) \(\mathrm{HSO}_{3}^{-}(a q)+\mathrm{H}_{3} \mathrm{O}^{+}(a q) \rightleftharpoons \mathrm{H}_{2} \mathrm{SO}_{3}(a q)+\mathrm{H}_{2} \mathrm{O}(l)\)

Short answer

(a) HBrO is the acid and H2O is the base; H3O+ is the conjugate acid and BrO- is the conjugate base. (b) HSO4- is the acid and HCO3- is the base; SO4²⁻ is the conjugate base and H2CO3 is the conjugate acid. (c) HSO3⁻ is the acid and H3O+ is the base; H2SO3 is the conjugate acid and H2O is the conjugate base.

Step-by-step solution

(a) Identify the acid and base on the left side

First, find which species is donating a proton (H+). In this case, HBrO is donating a proton to H2O, so HBrO is the acid and H2O is the base.

(a) Identify the conjugate acid and conjugate base on the right side

After the proton (H+) transfer, we can see that the products are H3O+ and BrO-. H3O+, being formed from the proton accepting species H2O, is the conjugate acid, and BrO- is the conjugate base.

(b) Identify the acid and base on the left side

In this equation, HSO4- is donating a proton to HCO3-, making HSO4- the acid and HCO3- the base.

(b) Identify the conjugate acid and conjugate base on the right side

After the proton transfer, the products are SO4²⁻ and H2CO3. SO4²⁻ is the conjugate base, having formed after HSO4- lost a proton, and H2CO3 is the conjugate acid, having gained a proton from the base HCO3-.

(c) Identify the acid and base on the left side

In this equation, HSO3- is donating a proton to H3O+, making HSO3- the acid and H3O+ the base.

(c) Identify the conjugate acid and conjugate base on the right side

After the proton transfer, the products are H2SO3 and H2O. H2SO3 is the conjugate acid, having gained a proton from the base H3O+, and H2O is the conjugate base, having lost a proton to HSO3-.

Key concepts

Conjugate Acid-Base Pairs

In the context of the Bronsted-Lowry acid-base theory, understanding conjugate acid-base pairs is crucial. A conjugate acid-base pair consists of two species that transform into each other by the gain or loss of a proton ( H^+ ). When an acid donates a proton, it forms its conjugate base, and when a base accepts a proton, it forms its conjugate acid. This concept plays a fundamental role in many chemical reactions.

Let's break it down using an example from the exercise:

• In equation (a), HBrO loses a proton to become BrO^−, making HBrO and BrO^− a conjugate acid-base pair.
• Similarly, H2O gains a proton to become H3O^+, forming another conjugate acid-base pair with H2O and H3O^+.

This pairing helps categorize substances during reactions, ensuring each has a counterpart when protons are exchanged. Understanding these relationships is pivotal in mastering acid-base chemistry.

Proton Transfer

Proton transfer is the heart of acid-base reactions according to the Bronsted-Lowry theory. It involves the movement of a proton ( H^+ ) from an acid, which donates it, to a base, which accepts it.

Consider equation (b) from the exercise:

• HSO4^- donates a proton to HCO3^-.
• This results in the formation of SO4^2^− and H2CO3.

This critical step means that for every acid, there must exist a corresponding base to accept and stabilize the proton in its new form.

Understanding proton transfer provides insight into the strength of acids and bases. The ease or difficulty with which a proton is transferred can tell us about the reactivity and stability of the involved substances.

Acid-Base Reactions

Acid-base reactions are a fundamental category of chemical reactions central to numerous processes in nature and industry. These reactions involve the exchange of protons between acids and bases.

Focusing on equation (c) from the exercise, HSO3^- and H3O^+ undergo a typical acid-base exchange:

• HSO3^- acts as an acid, donating a proton to H3O^+.
• H3O^+ serves as a base, accepting that proton.

After the reaction, the products H2SO3 and H2O can be recognized as the conjugate acid and base, respectively.

Such reactions create substances that often have very different properties from the reactants. Observing these changes helps chemists predict reaction outcomes and manipulate conditions to achieve the desired results, proving the versatility and utility of acid-base chemistry.