Question

Classify each of the following aqueous solutions as a nonelectrolyte, weak electrolyte, or strong electrolyte: (a) \(\mathrm{PbCl}_{2}\), (b) \(\mathrm{N}\left(\mathrm{CH}_{3}\right)_{3}\), (c) \(\mathrm{CsOH}\) (d) \(\mathrm{H}_{2} \mathrm{~S}\), (e) \(\mathrm{CrCl}_{2}\) (f) \(\mathrm{Ni}\left(\mathrm{CH}_{3} \mathrm{COO}\right)_{2}\)

Short answer

(a) Weak electrolyte, (b) Weak electrolyte, (c) Strong electrolyte, (d) Weak electrolyte, (e) Strong electrolyte, (f) Strong electrolyte.

Step-by-step solution

Understand Electrolytes

Electrolytes are substances that dissolve in water to produce ions, conducting electricity. Strong electrolytes dissociate completely into ions, weak electrolytes partially dissociate, and nonelectrolytes do not dissociate at all.

Analyzing Lead Chloride  (PbCl_2)

Lead chloride is a slightly soluble salt, meaning only a small amount dissolves and dissociates into ions in water. Thus, it is a weak electrolyte because of its limited ion formation.

Analyzing Trimethylamine  (N(CH_3)_3)

Trimethylamine is a weak base. When dissolved in water, it accepts a proton and partially ionizes, forming ions. Thus, it is classified as a weak electrolyte.

Analyzing Cesium Hydroxide  (CsOH)

Cesium hydroxide is a strong base and fully dissociates into cesium and hydroxide ions in water. Therefore, it is classified as a strong electrolyte.

Analyzing Hydrogen Sulfide  (H_2S)

Hydrogen sulfide is a weak acid that partially dissociates into hydrogen and sulfide ions in water, making it a weak electrolyte.

Analyzing Chromium (II) Chloride  (CrCl_2)

Chromium (II) chloride is a salt that dissociates completely in water, like many chlorides, so it is considered a strong electrolyte.

Analyzing Nickel (II) Acetate  (Ni(CH_3COO)_2)

Nickel (II) acetate dissociates in water to form nickel ions and acetate ions. As it dissociates completely, it is classified as a strong electrolyte.

Key concepts

Nonelectrolyte

When a substance dissolves in water but does not produce any ions, it is called a nonelectrolyte. Nonelectrolytes do not conduct electricity in aqueous solutions.
For instance, common household substances like sugar or urea dissolve in water, but they do not form ions.

• In such solutions, the molecules stay together and do not separate into charged particles.
• This means the solution does not carry an electrical current.

Understanding nonelectrolytes is important in distinguishing them from substances that can conduct electricity when dissolved in water.

Weak Electrolyte

Weak electrolytes are substances that only partially dissociate into ions when dissolved in water. This means they conduct electricity weakly.
When you dissolve a weak electrolyte in water, only a small fraction of its molecules split into ions. The rest remain intact.

• Examples of weak electrolytes include acetic acid and ammonia.
• In the given exercise, substances like \(\text{N(CH}_3\text{)}_3\) and \(\text{H}_2\text{S}\) fall into this category due to their limited ionization.

Knowing about weak electrolytes helps in understanding how different substances influence the conductivity of solutions.

Strong Electrolyte

Strong electrolytes completely dissociate into ions when they dissolve in water. This complete ionization allows the solution to conduct electricity very well.
Strong acids, strong bases, and most salts fall under this category.

• Common examples include sodium chloride (NaCl) and sulfuric acid (\(\text{H}_2\text{SO}_4\)).
• In the textbook exercise, \(\text{CsOH}\) and \(\text{CrCl}_2\) are strong electrolytes as they fully dissociate, producing a high concentration of ions.

Understanding strong electrolytes is crucial for predicting how substances will behave in water as they significantly affect the solution's electrical conductivity.

Aqueous Solutions

An aqueous solution is formed when a substance dissolves in water. The water serves as the solvent in these solutions.
Water's ability to dissolve a wide range of substances makes it a universal solvent. This is why so many chemical reactions take place in aqueous solutions.

• When substances dissolve, they can either form a molecular solution or dissociate into ions.
• The behavior of dissolved substances can vary greatly and is key to categorizing them as electrolytes or nonelectrolytes.

Aqueous solutions are a fundamental concept in chemistry, helping to understand how different substances interact with water and each other.

Dissociation

Dissociation is the process of a compound separating into its constituent ions when dissolved in water.
This process is crucial for understanding how substances behave in solution.

• In strong electrolytes, dissociation occurs completely, resulting in free ions that conduct electricity well.
• Weak electrolytes only partially dissociate, leading to a balance between intact molecules and ions in solution.
• Nonelectrolytes do not dissociate at all when dissolved.

The degree of dissociation is a key criterion in classifying substances as strong, weak, or non-electrolytes, and it significantly influences the properties of the solution.