Problem 13 - Chemistry The Central Science

Question

State whether each of the following statements is true or false. Justify your answer in each case. \begin{equation} \begin{array}{l}{\text { (a) Electrolyte solutions conduct electricity because elec- }} \\ {\text { trons are moving through the solution. }} \\ {\text { (b) If you add a nonelectrolyte to an aqueous solution that }} \\ {\text { already contains an electrolyte, the electrical conduc- }} \\ {\text { tivity will not change. }}\end{array} \end{equation}

Step-by-Step Solution

Answer

Statement (a): False. Electrolyte solutions conduct electricity due to the movement of ions in the solution, not electrons. Statement (b): False. Adding a nonelectrolyte to an electrolyte solution will cause a decrease in the electrical conductivity, as the additional molecules interfere with the movement of the electrolyte's ions.

Step 1: Statement (a):

Electrolyte solutions conduct electricity because electrons are moving through the solution. First, we need to understand that electrolyte solutions are solutions with dissolved ions. These ions are responsible for the electrical conductivity of the solution. The statement is claiming that the conductivity comes from electrons moving through the solution. This statement is false. Although electrons are responsible for electrical conductivity in metals, electrolyte solutions conduct electricity due to the movement of ions in the solution. When an electrical potential is applied across the solution, the ions will move towards the opposite charges, leading to the flow of electricity.

Step 2: Statement (b):

If you add a nonelectrolyte to an aqueous solution that already contains an electrolyte, the electrical conductivity will not change. A nonelectrolyte is a substance that does not conduct electricity when dissolved in water. This is because it does not break up into ions in solution. Now we are assessing the impact of adding a nonelectrolyte to a solution with an electrolyte already in it. This statement is false. When a nonelectrolyte is added to an electrolyte solution, the additional molecules will interfere with the movement of the electrolyte's ions. Thus, the original ions are less able to move freely, causing a decrease in the electrical conductivity.

Key Concepts

Ions in Solution

In electrolyte solutions, the key players responsible for conducting electricity are ions. These ions are charged atoms or molecules that have lost or gained electrons. Once dissolved in water, electrolytes like salts, acids, and bases dissociate into positively and negatively charged ions. This dissociation is a defining feature of electrolyte solutions.

When you introduce an electrical potential across such a solution, the ions begin to migrate towards electrodes: cations (positively charged) travel to the negative electrode, while anions (negatively charged) move to the positive electrode. This movement of ions under electrical influence is what causes the flow of current in an electrolyte solution.

It is crucial to note that, unlike metals where electrons flow to conduct electricity, in electrolyte solutions, it is the ions that carry charge across the solution. The understanding of this concept helps clarify the mechanism behind electrical conductivity in various aqueous solutions.

Nonelectrolyte

A nonelectrolyte is a substance that, when dissolved in water, does not produce ions. This means it doesn’t contribute to the electrical conductivity of the solution. Common examples of nonelectrolytes include sugar and ethanol.

Why don't nonelectrolytes conduct electricity? The answer resides in their molecular nature. Unlike electrolytes, nonelectrolytes dissolve without dissociating into ions. They remain whole molecules in solution, lacking the charged particles necessary for conducting electricity. Here’s a closer look:

• Nonelectrolytes do not ionize in solution.
• They exhibit molecular dissolution instead of ionic dissociation.

If you add a nonelectrolyte like sugar to a solution containing dissolved ions (electrolyte), the sugar molecules can interrupt the movement of the ions. This can cause a decrease in the overall electrical conductivity, as it impedes the free movement of ions necessary for conducting electricity.

Electrical Conductivity

Electrical conductivity in solutions arises primarily due to the movement of ions. It's a fascinating property that depends on several factors, including the concentration and type of ions present in the solution.

Here's how electrical conductivity works in an aqueous solution:

• Conductivity increases with a higher concentration of ions.
• Different ions have different mobilities and can impact conductivity variably.

The presence of ions and their ability to move directly translates to how well a solution can conduct electricity.

When considering electrical conductivity, it's essential to differentiate between strong and weak electrolytes:

• Strong electrolytes fully dissociate in solution, producing a high concentration of ions, which enabled increased conductivity.
• Weak electrolytes only partially dissociate, resulting in fewer ions available to conduct electrical current, thus reducing conductivity.

Substances like salts (e.g., sodium chloride) are often strong electrolytes, while substances like acetic acid are examples of weak electrolytes. Only solutions with significant ionic content can effectively conduct electricity, distinguishing electrolytes from nonelectrolytes.