Problem 37 - Chemistry: The Central Science

Question

Classify each of the following substances as a nonelectrolyte, weak electrolyte, or strong electrolyte in water: (a) \(\mathrm{H}_{2} \mathrm{SO}_{3}\), (b) \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}\) (ethanol), (c) \(\mathrm{NH}_{3}\), (d) \(\mathrm{KClO}_{3}\) (e) \(\mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2}\)

Step-by-Step Solution

Answer

(a) H2SO3: weak electrolyte, (b) C2H5OH (ethanol): nonelectrolyte, (c) NH3: weak electrolyte, (d) KClO3: strong electrolyte, (e) Cu(NO3)2: strong electrolyte.

Step 1: (a) Classify H2SO3 as a nonelectrolyte, weak electrolyte, or strong electrolyte)

H2SO3, also known as sulfurous acid, is a weak acid in an aqueous solution. It partially dissociates into ions, meaning it's a weak electrolyte.

Step 2: (b) Classify C2H5OH as a nonelectrolyte, weak electrolyte, or strong electrolyte)

C2H5OH, also known as ethanol, is not an acid or a base, and it does not dissociate into ions when dissolved in water. Therefore, it is a nonelectrolyte.

Step 3: (c) Classify NH3 as a nonelectrolyte, weak electrolyte, or strong electrolyte)

NH3, also known as ammonia, is a weak base in an aqueous solution. It reacts with water and partially dissociates into its ions, meaning it's a weak electrolyte.

Step 4: (d) Classify KClO3 as a nonelectrolyte, weak electrolyte, or strong electrolyte)

KClO3, also known as potassium chlorate, is a salt that fully dissociates into its ions when dissolved in water. Thus, it is a strong electrolyte.

Step 5: (e) Classify Cu(NO3)2 as a nonelectrolyte, weak electrolyte, or strong electrolyte)

Cu(NO3)2, also known as copper(II) nitrate, is a salt that dissolves completely into its ions when dissolved in water. Therefore, it is a strong electrolyte.

Key Concepts

Nonelectrolyte

Substances that don't separate into ions when dissolved in water are called nonelectrolytes. These compounds do not conduct electricity when in an aqueous solution. Ethanol, or \[\mathrm{C}_{2}\mathrm{H}_{5}\mathrm{OH}\]is a common example of a nonelectrolyte. When you dissolve ethanol in water, it stays intact as neutral molecules.

Nonelectrolytes can dissolve in water, but they do not change into ions. This is why solutions of nonelectrolytes do not conduct electricity. Everyday examples include most organic compounds like sugar and urea.

Weak Electrolyte

Weak electrolytes are substances that only partially separate into ions in water. As a result, they conduct electricity poorly. A well-known weak electrolyte is ammonia, \[\mathrm{NH}_3\],which becomes partially ionized in water to produce some ions.

Many weak acids and weak bases fall into this category. They are not 100% converted into ions, leading to a balance between the ions and the original molecules in the solution.

• Sulfurous acid \[\mathrm{H}_{2}\mathrm{SO}_{3}\] is also a weak electrolyte when it partially dissociates into ions.

Strong Electrolyte

Strong electrolytes are substances that completely break down into ions in water. They're very good at conducting electricity. Potassium chlorate, \[\mathrm{KClO}_3\],and copper(II) nitrate, \[\mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2}\],are examples of strong electrolytes.

In an aqueous solution, strong electrolytes become fully ionized. They're usually strong acids, strong bases, and most salts.

• Since they release a high concentration of ions into the solution, they facilitate the flow of electrical current.

Aqueous Solution

When a substance is dissolved in water, it forms an aqueous solution. The word 'aqueous' signifies that water is the solvent. In aqueous solutions, the behavior of solutes can be dependent on their nature.

Water is known as the "universal solvent" because it dissolves more substances than any other liquid. Its ability to dissolve solutes so well makes it perfect for forming solutions like acids, bases, and salts.

• The properties of a solution, such as conductivity, depend on whether the solute is a nonelectrolyte, weak electrolyte, or strong electrolyte.

Dissociation

Dissociation refers to the process where compounds separate into smaller components, typically ions, when dissolved in water. It’s a key concept in understanding electrolytes as it determines how well a substance can conduct electricity.

In some cases, like with strong electrolytes, dissociation is complete, resulting in numerous ions. For weak electrolytes, dissociation is only partial; not all molecules break into ions.

• Nonelectrolytes do not undergo dissociation, remaining as whole molecules in solutions.

Understanding dissociation helps predict whether a solution can conduct electricity and to what extent.