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) \(\mathrm{LiClO}_{4}\): Lithium perchlorate

Since \(\mathrm{LiClO}_{4}\) is an ionic compound, when it dissolves in water, it disperses as \(\mathrm{Li^{+}}\) and \(\mathrm{ClO_4^{-}}\) ions. This complete dissociation makes \(\mathrm{LiClO}_{4}\) a strong electrolyte.

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

Hypochlorous acid, \(\mathrm{HClO}\), only partially dissociates in water to form \(\mathrm{H^{+}}\) and \(\mathrm{ClO^{-}}\) ions. Since its dissociation is not complete, it is classified as a weak electrolyte.

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

Propanol is an organic compound and does not dissociate into ions when dissolved in water. Therefore, it is a nonelectrolyte.

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

Chloric acid, \(\mathrm{HClO}_{3}\), is a strong acid that completely dissociates in water to form \(\mathrm{H^{+}}\) and \(\mathrm{ClO_3^{-}}\) ions. Therefore, it is a strong electrolyte.

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

Copper(II) sulfate, \(\mathrm{CuSO}_4\), is an ionic compound that dissociates completely in water into \(\mathrm{Cu^{2+}}\) and \(\mathrm{SO_4^{2-}}\) ions. This makes it a strong electrolyte.

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

Sucrose is an organic compound and does not dissociate into ions when dissolved in water. Therefore, it is a nonelectrolyte. In conclusion, the given compounds are classified as follows: - (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

Key Concepts

Strong Electrolytes

Substances that completely dissociate into ions when dissolved in water are classified as strong electrolytes. This process involves an ionic compound splitting into its constituent cations and anions. For example, when lithium perchlorate (\r\(\mathrm{LiClO}_{4}\)\r) enters a solution, it separates into lithium ions (\r\(\mathrm{Li^{+}}\)\r) and perchlorate ions (\r\(\mathrm{ClO_4^{-}}\)\r). Such a high degree of ionization in water allows the solution to conduct electricity very effectively, hence the term 'electrolyte'. Strong acids like chloric acid (\r\(\mathrm{HClO}_{3}\)\r) and ionic salts such as copper(II) sulfate (\r\(\mathrm{CuSO}_4\)\r) are also strong electrolytes, as they too completely break down into ions.\r

Strong electrolytes have a few distinctive properties:\r

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• They are often soluble ionic compounds.
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• They contribute to high conductivity of the solution.
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• They ensure the solution contains a large number of free ions.
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\rThese properties make strong electrolytes overly efficient in electrical transmission and are fundamental in various industrial and biological processes.

Weak Electrolytes

Weak electrolytes are compounds that partially dissociate into ions in a solution. The key word here is 'partially'; not all molecules of the solute release ions. A great example of this is hypochlorous acid (\r\(\mathrm{HClO}\)\r), which dissociates into hydrogen ions (\r\(\mathrm{H^{+}}\)\r) and hypochlorite ions (\r\(\mathrm{ClO^{-}}\)\r) but only to a limited extent. Because of the incomplete dissociation, solutions with weak electrolytes conduct electricity poorly compared to strong electrolytes.\r

Here are some important points about weak electrolytes:\r

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• They typically include weak acids and bases.
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• Only a fraction of solute molecules ionize in water.
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• The electrical conductivity of the solution is relatively low.
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\rBeing partially ionizable, weak electrolytes are crucial in maintaining equilibrium in various chemical reactions and biological systems.

Nonelectrolytes

Now let's discuss nonelectrolytes, which are compounds that do not produce ions when dissolved in water. This means they do not conduct electricity, as they do not release any charged particles that would carry an electrical current. Organic compounds such as propanol (\r\(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OH}\)\r) and sucrose (\r\(\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}\)\r) are typical nonelectrolytes. Despite being soluble in water, these compounds do not break apart into ions; they stay intact as total molecules.\r

A few characteristics of nonelectrolytes include:\r

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• They are often covalent compounds.
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• Their solutions do not conduct electricity.
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• They are present as whole molecules in the solution, not as cations and anions.
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\rUnderstanding nonelectrolytes helps to explain why not all solutes can conduct electricity and proves essential in understanding various chemical interaction dynamics.

Ionic Dissociation

Ionic dissociation is a process where an ionic solid dissolves in a solvent and separates into its constituent ions. The ability of a compound to undergo ionic dissociation determines if it's a strong or weak electrolyte, or a nonelectrolyte. This concept is a cornerstone in chemistry because it describes how substances interact with water to produce ions, which are the key players in creating electrically conducting solutions.\r

To illustrate, when we dissolve sodium chloride (\r\(\mathrm{NaCl}\)\r) in water, this table salt undergoes ionic dissociation to form sodium (\r\(\mathrm{Na^{+}}\)\r) and chloride (\r\(\mathrm{Cl^{-}}\)\r) ions. It's this generation of free ions that allows the solution to carry an electric current.\r

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• Strong electrolytes dissociate completely into ions.
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• Weak electrolytes dissociate partially, creating fewer ions.
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• Nonelectrolytes do not dissociate into ions at all.
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\rUnderstanding ionic dissociation has profound implications in fields such as material science, electrochemistry, and pharmacology, where ion behavior in solution is critically important.