Problem 57 - Chemistry Matter and Change

Question

Down's Cell What reaction takes place at the cathode when molten sodium chloride is electrolyzed?

Step-by-Step Solution

Answer

The reduction of sodium ions at the cathode forms sodium metal: \( \text{Na}^+ + e^- \rightarrow \text{Na} \).

Step 1: Understand the Electrolysis Process

Electrolysis is a process in which electrical energy is used to drive a non-spontaneous chemical reaction. In the case of molten sodium chloride (NaCl), the process results in the separation of sodium ions (Na⁺) and chloride ions (Cl⁻).

Step 2: Identify the Cathode and Anode

In an electrolytic cell, the cathode is the electrode where reduction occurs, and the anode is where oxidation occurs. For molten NaCl, the cathode is where Na⁺ ions gain electrons.

Step 3: Determine the Cathode Reaction

The cathode reaction involves the reduction of sodium ions. The Na⁺ ions in the molten state will migrate to the cathode, where they will gain electrons (e⁻) to form metallic sodium (Na).

Step 4: Write the Cathode Reaction Equation

The equation for the reaction at the cathode can be written as: \[ \text{Na}^+ + e^- \rightarrow \text{Na} \] This equation shows the reduction of sodium ions to form sodium metal at the cathode.

Key Concepts

Molten sodium chloride

Molten sodium chloride, commonly represented as NaCl, is an ionic compound consisting of sodium ions (\(\text{Na}^+\) ) and chloride ions (\(\text{Cl}^-\)). When NaCl is molten, it is in a liquid state, allowing the ions to move freely.
In this state, the structure of sodium chloride changes significantly, drastically differing from its solid crystalline form.The process of electrolysis requires that the ionic compound be molten or in solution to enable the movement of ions to the electrodes.The molten state is crucial for electrolysis as it allows the ions to conduct electricity by moving toward their respective electrodes. This movement facilitates the separation of elemental sodium from sodium chloride during the electrolysis process.
Overall, the molten state of NaCl is essential for the separation of its elemental components and the completion of redox reactions.

Cathode reaction

In electrolysis, the cathode is the electrode where reduction, the gain of electrons, occurs. During the electrolysis of molten sodium chloride, the cathode plays a critical role in converting ions into neutral elements.Sodium ions (\(\text{Na}^+\)) travel through the molten mixture towards the cathode because it is negatively charged. Upon reaching the cathode, these ions undergo reduction.Reduction is characterized by the gain of electrons. The reaction can be represented as:\[ \text{Na}^+ + e^- \rightarrow \text{Na} \]This equation illustrates the gain of one electron by a sodium ion, resulting in the formation of sodium metal. Such transformation emphasizes how the cathode aids in achieving electrochemical reactions during the electrolysis.
Ultimately, understanding the cathode reaction enriches comprehension of the processes within electrolytic cells.

Reduction of sodium ions

Reduction of sodium ions is a critical component of the electrolysis of molten sodium chloride. In the context of electrolysis, reduction refers to the chemical change where ions gain electrons.For molten NaCl, the sodium ions (\(\text{Na}^+\)) approach the cathode and participate in the following reaction:\[ \text{Na}^+ + e^- \rightarrow \text{Na} \]This formula tells us that each sodium ion requires one electron to be reduced into sodium metal. The electron comes from the external circuit supplying the electrolytic cell, allowing the reduction process to take place.The importance of this reduction cannot be understated. It transforms ionic, electrically charged sodium into pure, neutral sodium metal ready for extraction and utilization.Understanding this process helps demystify how electrical energy plays a role in driving chemical reactions to yield new substances.

Down's Cell

The Down's Cell is an industrial apparatus specifically designed for the electrolytic extraction of sodium metal from sodium chloride. This cell contains molten sodium chloride and typically operates at temperatures above 800°C to maintain the salt’s molten state. Within the Down's Cell, graphite is used as the anode, and the steel container acts as the cathode. Important features of Down's Cell include:

• An efficient method of extracting sodium, catering to large-scale industrial needs.
• Capability to manage high temperatures necessary to keep sodium chloride in a liquid state.
• An isolated chamber for handling the reactive sodium metal produced during electrolysis.

The Down's Cell is crucial for industries needing metallic sodium. It underscores the significance of electrochemical processes in modern chemistry, demonstrating how technological advancements utilize these reactions for manufacturing purposes.