Problem 115 - Introductory Chemistry Atoms First

Question

To be a weak base in water, a molecular compound must also be a weak electrolyte. What must be one of the ions it produces in water?

Step-by-Step Solution

Answer

One of the ions produced by a weak base when it acts as a weak electrolyte in water must be the hydroxide ion (OH-).

Step 1: Understand weak bases and weak electrolytes

A weak base is a substance that does not completely ionize or dissociate in water to produce hydroxide ions (OH-) and its conjugate acid. A weak electrolyte is a substance that partially dissociates into its constituent ions in water, and thus does not conduct electricity as efficiently as a strong electrolyte.

Step 2: Identify a common ion produced by weak bases in water

When weak bases dissolve in water, they partially ionize, producing hydroxide ions (OH-) and conjugate acid ions. One of the ions produced by a weak base in water is the hydroxide ion (OH-).

Step 3: Answer the question

One of the ions produced by a weak base when it acts as a weak electrolyte in water must be the hydroxide ion (OH-).

Key Concepts

Weak Electrolytes

Weak electrolytes are substances that do not fully dissociate into ions when dissolved in water. This means that these compounds only partially break apart, leaving a significant portion of the original molecules intact in the solution. This incomplete dissociation leads to weak electrolytes being poor conductors of electricity.

• Examples of weak electrolytes include many weak acids and bases, such as acetic acid and ammonia.
• Weak electrolytes exhibit equilibrium behavior, meaning they can exist in both ionized and non-ionized forms in solution.

Understanding the behavior of weak electrolytes is crucial in chemistry because it helps explain why certain substances may be less effective in driving electrical or chemical processes compared to their strong counterparts. The partial ionization impacts reaction rates and conductivities in solutions.

Hydroxide Ions

Hydroxide ions ( OH ext{-} ) play a key role in determining the basicity of a substance. When a base dissolves in water, it typically forms hydroxide ions, which are responsible for the basic nature of the solution.

• The presence of hydroxide ions in a solution indicates an increase in pH, making the solution more basic or alkaline.
• In the case of weak bases, the formation of hydroxide ions is limited, as not all the base molecules dissociate fully.

These ions are vital in various chemical reactions, such as neutralization reactions, where they react with hydrogen ions ( H^+ ) to form water. Understanding hydroxide ions is essential for studying the behavior of basic solutions and predicting the outcomes of reactions involving bases.

Ionization in Water

Ionization in water refers to the process whereby molecules split into ions when dissolved in water. This process is crucial in understanding the behavior of acids and bases.

• In weak bases, ionization is incomplete, meaning only a small fraction of the molecules convert into ions.
• This partial ionization is what characterizes a substance as a weak electrolyte.

Ionization influences several important properties of a solution:

• Conductivity: Solutions with fully ionized substances conduct electricity well, while those with partially ionized substances, like weak bases, do not.
• pH levels: The extent of ionization affects the acidity or basicity of a solution, impacting chemical equilibria.

Understanding ionization is key for predicting and explaining how substances behave in aqueous solutions, be it in biological, environmental, or industrial contexts.