Question

When dissolved in water, a(n) _______ donates \(\mathrm{H}^{+} ;\) \(\mathrm{a}(\mathrm{n})\) ________ accepts \(\mathrm{H}^{+}\). a. acid; base b. base; acid c. buffer; solute d. base; buffer

Short answer

The correct answer is (a) acid; base.

Step-by-step solution

Identify Key Concepts

Understand that the question refers to substances in water that either donate or accept hydrogen ions (\(\mathrm{H}^+\)). These concepts are tied to acid-base chemistry, where acids donate \(\mathrm{H}^+\) ions and bases accept them.

Define Acids and Bases

An acid is a substance that donates \(\mathrm{H}^+\) ions when dissolved in water, while a base is a substance that accepts \(\mathrm{H}^+\) ions.

Match the Definitions

Based on the definitions: - '_______ donates \(\mathrm{H}^{+}\)' matches the definition of an acid.- '_______ accepts \(\mathrm{H}^{+}\)' matches the definition of a base.

Choose the Correct Answer

Considering the matched definitions from Step 3, the correct option is (a) acid; base, as it correctly pairs the ability to donate \(\mathrm{H}^+\) with an acid and the ability to accept \(\mathrm{H}^+\) with a base.

Key concepts

Understanding the Concept of an Acid

In acid-base chemistry, the term 'acid' refers to a substance that donates hydrogen ions (denoted as \(H^{+}\)) when it is dissolved in water. This characteristic of donating H^{+} ions is what classifies a molecule as an acid. For instance, when hydrochloric acid (HCl) is dissolved in water, it dissociates to release H^{+} ions.
Key Characteristics of Acids:

• Acids increase the concentration of H^{+} ions in a solution.
• They typically have a sour taste and can conduct electricity in solution.
• Acids can be strong, like sulfuric acid (H₂SO₄), which completely dissociates in water, or weak, like acetic acid (CH₃COOH), which only partially dissociates.

Understanding acids is crucial for grasping how they interact with bases to form salts and water through neutralization reactions. This donation of \(H^{+}\) ions is a fundamental concept that helps predict the behavior of acids in various chemical processes.

Exploring the Role of a Base

A 'base' is a substance that accepts H^{+} ions in a solution, thus decreasing the concentration of hydrogen ions. When a base is dissolved in water, it can either directly absorb H^{+} ions or indirectly increase basicity through the generation of hydroxide ( OH^{-} ) ions.
Characteristics of Bases:

• Bases typically have a bitter taste and a slippery feel.
• They can neutralize acids by accepting H^{+} ions from them.
• Examples include sodium hydroxide (NaOH), which dissociates into Na⁺ and OH⁻ ions in water, effectively removing H^{+} ions from the solution.

Bases play an essential role in maintaining pH balance in solutions and have wide applications, from household cleaning agents to biological systems where they help buffer pH levels. Recognizing how bases work by accepting hydrogen ions provides valuable insight into their fundamental chemical behavior.

The Importance of Hydrogen Ions

The hydrogen ion, H^{+} , is central to the study of acid-base chemistry. Simply put, it is a proton that plays a critical role in defining the acidic or basic nature of a solution. When acids dissolve in water, they release H^{+} ions, which increases the acidity of the solution. Conversely, bases reduce acidity by either absorbing these ions or increasing the presence of hydroxide ions, which combine with hydrogen ions to form water.
Relevance of Hydrogen Ions:

• The concentration of H^{+} ions in a solution is used to determine its pH, a scale that measures acidity or basicity.
• A high concentration of H^{+} ions indicates a low pH, characteristic of acidic solutions, while a low H^{+} concentration corresponds to a high pH, indicative of basic (alkaline) solutions.
• In biological systems, the precise regulation of H^{+} concentrations is vital for processes such as enzyme activity and cellular respiration.

Understanding hydrogen ions is key to mastering more complex topics in chemistry, as they are foundational to reactions and processes that govern both synthetic and natural systems.