Question

Write the following salts in either the ionized or the nonionized form to best represent an aqueous solution: (a) \(\mathrm{AlPO}_{4}(s)\) (b) \(\mathrm{Co}\left(\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{2}\right)_{3}(a q)\) (c) \(\mathrm{MnSO}_{4}(a q)\) (d) \(\mathrm{PbSO}_{4}(s)\)

Short answer

(a) \(\mathrm{AlPO}_{4}(s)\); (b) ionized: \(\mathrm{Co}^{3+} + 3\mathrm{CH}_{3}\mathrm{COO}^{-}\); (c) ionized: \(\mathrm{Mn}^{2+} + \mathrm{SO}_{4}^{2-}\); (d) \(\mathrm{PbSO}_{4}(s)\).

Step-by-step solution

Understanding Ionization

In an aqueous solution, salts can either exist in ionized form (dissociated into ions) or in nonionized form (remains as a whole).

Analyzing Aluminum Phosphate (AlPO4)

Aluminum phosphate, \(\mathrm{AlPO}_{4}\), is insoluble in water and remains largely undissolved as a solid. Hence, it is best represented in its nonionized form \(\mathrm{AlPO}_{4}(s)\) in an aqueous solution.

Analyzing Cobalt(III) Acetate \(\mathrm{Co}\left(\mathrm{C}_{2}\mathrm{H}_{3}\mathrm{O}_{2}\right)_{3}\)

Cobalt(III) acetate is soluble in water, meaning it dissociates into its ions in an aqueous solution. It is best represented in ionized form: \(\mathrm{Co}^{3+}(aq) + 3\mathrm{CH}_{3}\mathrm{COO}^{-}(aq)\).

Analyzing Manganese(II) Sulfate (MnSO4)

Manganese(II) sulfate is soluble in water and dissociates into ions. It is best represented in ionized form: \(\mathrm{Mn}^{2+}(aq) + \mathrm{SO}_{4}^{2-}(aq)\).

Analyzing Lead(II) Sulfate (PbSO4)

Lead(II) sulfate is largely insoluble in water and remains as a solid. Therefore, it is best represented in its nonionized form \(\mathrm{PbSO}_{4}(s)\) in an aqueous solution.

Key concepts

Solubility of Salts

Understanding the solubility of salts is fundamental to predicting their behavior in aqueous solutions. Solubility refers to the ability of a solute, in this case a salt, to dissolve in a solvent, such as water. If a salt is soluble, it dissociates into its constituent ions which are then distributed throughout the solvent. If a salt is insoluble, it typically does not dissolve and remains as a solid.
Factors that impact solubility include:

• Nature of the salt: Different salts have varying levels of solubility in water. For instance, some compounds like sodium chloride dissolve readily, while others like aluminum phosphate, (\(\mathrm{AlPO}_{4}\)), do not dissolve and remain solid.
• Temperature: Generally, the solubility of solids in liquids increases with rising temperatures. However, this is not a universal rule for every salt.

In our context:
(a) \(\mathrm{AlPO}_{4}\) is practically insoluble, so it stays in nonionized form.
(b) \(\mathrm{Co}\left(\mathrm{C}_{2}\mathrm{H}_{3}\mathrm{O}_{2}\right)_{3}\) and (c) \(\mathrm{MnSO}_{4}\) are soluble and thus appear in ionized form in solutions.
(d) \(\mathrm{PbSO}_{4}\) remains mostly as a solid due to its low solubility, represented in its nonionized form again.

Chemical Dissociation

Chemical dissociation occurs when molecules or compounds separate into smaller particles, such as ions, in a solution. This is particularly significant for salts in water, resulting in electrolytic solutions that can conduct electricity:

• Dissociation Process: When salts like \(\mathrm{MnSO}_{4}\) dissolve in water, they dissociate into their respective ions: \(\mathrm{Mn}^{2+}(aq)\) and \(\mathrm{SO}_{4}^{2-}(aq)\). This ionization is essential in how solutions conduct electricity.
• Influence of Solvent: Water, a polar molecule, is highly effective at pulling ions apart and dissolving ionic compounds like \(\mathrm{Co}\left(\mathrm{C}_{2}\mathrm{H}_{3}\mathrm{O}_{2}\right)_{3}\), leading to \(\mathrm{Co}^{3+}\) and \(\mathrm{CH}_{3}\mathrm{COO}^{-}\) ions in solution.

Some salts like \(\mathrm{AlPO}_{4}\) and \(\mathrm{PbSO}_{4}\) don't dissociate significantly due to their low solubility, remaining largely in solid form, indicating minimal ionization in water.

Chemical Representation in Solutions

Chemical representation is crucial to understanding how substances behave in solutions—whether they are in ionized or nonionized states:
In an aqueous setting:

• Ionized Form: Soluble salts dissociate into ions, showing their chemical formulas in ionic representation. For example, \(\mathrm{Co}\left(\mathrm{C}_{2}\mathrm{H}_{3}\mathrm{O}_{2}\right)_{3}\) expresses as \(\mathrm{Co}^{3+}(aq) + 3\mathrm{CH}_{3}\mathrm{COO}^{-}(aq)\) in solution.
• Nonionized Form: For insoluble salts such as \(\mathrm{AlPO}_{4}(s)\) or \(\mathrm{PbSO}_{4}(s)\), a solid symbol '(s)' is maintained to indicate that these salts largely do not dissolve and stay undissociated in a solution.

These representations are not just academic symbols; they reveal the chemical nature and behavior of compounds in solutions, aiding in predicting reactions and behaviors in laboratory or practical applications.