Problem 11 - Biology: Concepts and Applications

Question

When dissolved in water, a(n) ______ donates \(\mathrm{H}^{+}\) \(a(n) ________ accepts \)H^{+}$.

Step-by-Step Solution

Answer

Acid donates H^+ ; base accepts H^+ .

Step 1: Understanding Acids and Bases

In chemistry, an acid is a substance that can donate a proton ( H^+ ) to another substance. This process is part of the Brønsted-Lowry theory of acids and bases.

Step 2: Definition of Base

According to the Brønsted-Lowry theory, a base is a substance that accepts a proton ( H^+ ) from another substance.

Step 3: Recognizing Acid in the Question

Identify the term in the question that corresponds to 'donates H^+ '. An acid is the substance that donates H^+ when dissolved in water.

Step 4: Recognizing Base in the Question

Identify the term in the question that corresponds to 'accepts H^+ '. A base is the substance that accepts H^+ in a reaction.

Key Concepts

Acid-Base Reactions

Acid-base reactions are a fundamental concept in chemistry that occur when an acid and a base interact to exchange protons. This exchange is central to the Brønsted-Lowry theory, which provides a broader understanding of acid-base behavior than previous definitions. In these reactions, the acid donates a proton ( H^+ ) to the base.
The reaction usually results in the formation of a conjugate base from the acid and a conjugate acid from the base. This interplay creates a dynamic equilibrium, allowing for reversible reactions. Understanding these transformations helps in predicting the outcome of reactions in solutions.
For example, in a simple acid-base reaction between hydrochloric acid (HCl) and ammonia (NH extsubscript{3}), HCl donates a proton to NH extsubscript{3}, resulting in ammonium ion (NH extsubscript{4}^+) and chloride ion (Cl^-).

• Acids donate protons.
• Bases accept protons.
• Conjugate acid-base pairs are always formed.

This concept is applied widely in fields like biology, environmental science, and industrial chemistry.

Proton Donor

In the context of the Brønsted-Lowry theory, a proton donor is another name for an acid. When we say a substance is an acid, we mean it has the ability to donate a proton to another substance. This ability is crucial in determining the strength of an acid.
The term proton donor simplifies the concept by highlighting the acid's role in these chemical reactions. When dissolved in water, the acid molecule releases an H^+ ion, leaving behind a conjugate base.
For example, in the reaction of acetic acid (CH extsubscript{3}COOH) in water, the acetic acid donates a proton, resulting in the formation of acetate ion (CH extsubscript{3}COO^-) and hydronium ion (H extsubscript{3}O^+).

• Acids can be strong or weak, influencing their ability to donate protons effectively.
• The more readily a compound donates a proton, the stronger the acid.
• Proton donation often results in a change of state, such as liquid to gas or liquid to solid depending on the reaction conditions.

This characteristic is at the heart of many chemical processes, from digestion in the human body to industrial manufacturing.

Proton Acceptor

According to the Brønsted-Lowry theory, a proton acceptor is called a base. Bases are capable of accepting H^+ ions from acids, making them essential reactants in acid-base reactions.
When we describe a substance as a proton acceptor, it underscores its role in creating a new chemical species during a reaction.
Bases, when dissolved in water, either dissociate to yield OH^- ions or directly accept protons from acids to form conjugate acids. For instance, when sodium hydroxide (NaOH) dissolves in water, it releases OH^- ions, which can accept protons to form water.

• The strength of a base is often judged by its ability to accept protons.
• Strong bases, like NaOH, completely dissociate in water.
• Weak bases only partially accept protons, which influences the equilibrium of reactions.

This concept is crucial for understanding processes such as buffering in biological systems and neutralization in chemical industries.