Problem 38 - Chemistry: The Central Science

Question

Classify each of the following aqueous solutions as a nonelectrolyte, weak electrolyte, or strong electrolyte: (a) \(\mathrm{LiClO}_{4}\), (b) \(\mathrm{HClO}\), (c) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OH}\) (propanol), (d) \(\mathrm{HClO}_{3}\), (e) \(\mathrm{CuSO}_{4}\), (f) \(\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}\) (sucrose).

Step-by-Step Solution

Answer

(a) \(\mathrm{LiClO}_{4}\): strong electrolyte, (b) \(\mathrm{HClO}\): weak electrolyte, (c) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OH}\) (propanol): nonelectrolyte, (d) \(\mathrm{HClO}_{3}\): strong electrolyte, (e) \(\mathrm{CuSO}_{4}\): strong electrolyte, (f) \(\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}\) (sucrose): nonelectrolyte.

Step 1: (a) \(\mathrm{LiClO}_{4}\)

This compound is a salt composed of the lithium ion (\(\mathrm{Li}^+\)) and the perchlorate ion (\(\mathrm{ClO}_4^-\)). When dissolved in water, it will dissociate completely into its constituent ions. Since it fully dissociates, \(\mathrm{LiClO}_{4}\) is a strong electrolyte.

Step 2: (b) \(\mathrm{HClO}\)

This compound is a weak acid (hypochlorous acid) that partially dissociates in water into its constituent ions: hydrogen ion (\(\mathrm{H}^+\)) and hypochlorite ion (\(\mathrm{ClO}^-\)). Since it only partially dissociates, \(\mathrm{HClO}\) is a weak electrolyte.

Step 3: (c) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OH}\) (propanol)

Propanol (an alcohol) does not dissociate into ions in water. This is because alcohols are covalent compounds, meaning they do not form ions. Thus, propanol is a nonelectrolyte.

Step 4: (d) \(\mathrm{HClO}_{3}\)

This compound is a strong acid (chloric acid) that dissociates completely in water into its constituent ions: hydrogen ion (\(\mathrm{H}^+\)) and chlorate ion (\(\mathrm{ClO}_3^-\)). Since it fully dissociates, \(\mathrm{HClO}_{3}\) is a strong electrolyte.

Step 5: (e) \(\mathrm{CuSO}_{4}\)

This compound is a salt composed of the copper ion (\(\mathrm{Cu}^{2+}\)) and the sulfate ion (\(\mathrm{SO}_4^{2-}\)). When dissolved in water, it will dissociate completely into its constituent ions. Since it fully dissociates, \(\mathrm{CuSO}_{4}\) is a strong electrolyte.

Step 6: (f) \(\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}\) (sucrose)

Sucrose, a sugar, does not dissociate into ions in water because it forms covalent bonds within its structure. Thus, sucrose is a nonelectrolyte.

Key Concepts

Nonelectrolytes

Nonelectrolytes are substances that, when dissolved in water, do not dissociate into ions. This means they do not conduct electricity. Typically, these substances are covalent compounds made up of nonmetals. Such compounds include sugars and certain alcohols.
For example, sucrose (\(\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}\)) and propanol (\(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OH}\)) are common nonelectrolytes. Although they dissolve in water, their molecules remain intact without generating ions.

• No ionization occurs in solution.
• Typically, nonconductors of electricity.
• Strong presence of covalent bonds.

These characteristics make nonelectrolytes easily identifiable in aqueous solutions.

Weak Electrolytes

Weak electrolytes, in contrast, partially dissociate into ions when dissolved in water. This partial dissociation means only some of their molecules break into ions, while others remain intact. As a result, weak electrolytes are poor conductors of electricity compared to strong electrolytes.
Hypochlorous acid (\(\mathrm{HClO}\)) is an example of a weak electrolyte. It partially dissociates in water to give hydrogen ions (\(\mathrm{H}^+\)) and hypochlorite ions (\(\mathrm{ClO}^-\)), yet a considerable portion of it remains as undissociated molecules.

• Partial ionization in solution.
• Limited electrical conductivity.
• Exist as a balance between dissociated ions and undissociated molecules.

Weak acids and some weak bases typically fall into this category of weak electrolytes.

Strong Electrolytes

Strong electrolytes are substances that completely dissociate into ions when dissolved in water. This complete dissociation allows strong electrolytes to conduct electricity very efficiently. They include strong acids, strong bases, and most salts.
For instance, \(\mathrm{LiClO}_{4}\) (lithium perchlorate) is a strong electrolyte because it dissociates completely to give lithium ions (\(\mathrm{Li}^+\)) and perchlorate ions (\(\mathrm{ClO}_4^-\)). Similarly, chloric acid (\(\mathrm{HClO}_{3}\)) and copper sulfate (\(\mathrm{CuSO}_{4}\)) are strong electrolytes due to their full ionization in aqueous solutions.

• Complete ionization occurs.
• High conductivity of electricity.
• Includes substances like strong acids, bases, and crystalline salts.

This reliable electrical power is why strong electrolytes are used in batteries and other electrical applications.

Ion Dissociation

Ion dissociation is a fundamental process where an ionic compound separates into individual ions when dissolved in a solvent like water. This process is crucial for the conductivity of electrolytes.
When a compound like \(\mathrm{CuSO}_{4}\) dissociates in water, it forms copper ions (\(\mathrm{Cu}^{2+}\)) and sulfate ions (\(\mathrm{SO}_4^{2-}\)).

• Involves breaking of ionic bonds in solids.
• Results in free-moving ions in solution.
• Essential for the functionality of electrolytes.

The extent of ion dissociation determines whether a substance is classified as a strong or weak electrolyte.

Covalent Compounds

Covalent compounds are characterized by atoms bonded together by shared electrons forming molecules. Unlike ionic compounds, covalent compounds do not dissociate into ions in a solution.
Substances like sucrose and propanol are covalent compounds, meaning their structure remains unchanged in water. Instead, they remain as molecules, which do not conduct electricity in a solution.

• Made up of molecules with shared electrons.
• Form nonelectrolytes when dissolved in water.
• Do not partake in ionization.

The molecular stability of covalent compounds is what distinguishes them from ionic compounds, impacting their roles in chemical reactions and solutions.