Problem 13 - Chemistry The Central Science In Si Units

Question

State whether each of the following statements is true or false. Justify your answer in each case. (a) Electrolyte solutions conduct electricity because electrons are moving through the solution. (b) If you add a nonelectrolyte to an aqueous solution that already contains an electrolyte, the electrical conductivity will not change.

Step-by-Step Solution

Answer

(a) False, because ions, not electrons, conduct electricity. (b) True, because nonelectrolytes do not affect ion concentration.

Step 1: Understanding Electrolyte Solutions

Electrolyte solutions conduct electricity due to the presence of ions. In these solutions, cations and anions carry electric current by moving through the solution, not electrons.

Step 2: Evaluating Statement (a)

Statement (a) is incorrect. In electrolyte solutions, the electric current is conducted by the movement of ions (charged particles), not electrons. Thus, stating that electrons move through the solution is false.

Step 3: Understanding Nonelectrolytes

Nonelectrolytes do not dissociate into ions when dissolved in water; they do not contribute to electrical conductivity. Adding them to a solution containing an electrolyte should not affect the total ion concentration.

Step 4: Evaluating Statement (b)

Statement (b) is true. Adding a nonelectrolyte to a solution already containing an electrolyte should not change the electrical conductivity, as nonelectrolytes do not provide additional ions that can carry a charge.

Key Concepts

Electrical Conductivity

Electrical conductivity refers to the ability of a substance to conduct electricity. In the context of solutions, it's crucial to understand that this happens due to the presence of charged particles, known as ions. These ions move through the solution, allowing electric current to pass.
Ions are produced when an electrolyte, such as salt, dissolves in water. The electrolyte dissociates into positive and negative ions, which are free to move around. This movement of ions is what allows the solution to conduct electricity.
It's a common misconception that electrons move through the solution to conduct electricity, but in fact, it's the ions that do the job.

• Ions are essential for conductivity.
• The solution needs movement of these ions to conduct electricity.

Thus, electrolyte solutions are good conductors of electricity due to the ion movement.

Nonelectrolytes

Nonelectrolytes are substances that, when dissolved in water, do not produce ions. Because they do not dissociate into charged particles, they do not contribute to the electrical conductivity of a solution.
Examples of nonelectrolytes include sugar and urea. These compounds dissolve in water, but their molecules remain intact and do not split into ions. As a result, adding a nonelectrolyte to a solution that already contains an electrolyte does not significantly change the electrical conductivity.

• Nonelectrolytes don't form ions in solutions.
• These substances do not help in conducting electricity.

Thus, a nonelectrolyte does not affect the electrical conductivity, reinforcing the understanding that the presence of ions is necessary for conducting electricity.

Ions in Solutions

Ions in solutions are the charged particles that enable the conduction of electricity. When an electrolyte dissolves in water, it breaks down into its constituent ions. For example, a salt like sodium chloride (NaCl) dissociates into sodium ions (Na⁺) and chloride ions (Cl^-).
These ions move freely in the solution, allowing them to carry electrical current through the liquid. The more ions that are present, the better the solution can conduct electricity. This is why a concentrated electrolyte solution conducts electricity more efficiently than a dilute one.

• Electrolytes dissociate into ions.
• More ions equate to better conductivity.

Understanding how ions function in solutions helps us grasp why some solutions are conductors and others are not.