Question

If sodium chloride (table salt) is melted and then subjected to an electric current, elemental gas is produced, along with sodium metal.

Short answer

In short, when molten sodium chloride (NaCl) is subjected to an electric current, electrolysis occurs. The positive sodium ions (Na^+) move to the negative electrode (cathode) and are reduced to form sodium metal (Na) with the reaction: \(Na^+ + e^- \to Na\). Meanwhile, negative chloride ions (Cl^−) move to the positive electrode (anode) and are oxidized to form elemental chlorine gas (Cl_2) with the reaction: \(2Cl^- \to Cl_2 + 2e^-\). Consequently, sodium metal and chlorine gas are produced.

Step-by-step solution

Melt the sodium chloride

First, we need to melt the sodium chloride (NaCl) to convert it from a solid-state into a liquid state. Melting the sodium chloride allows its ions to move freely in the liquid, which is essential for the electrolysis process to occur.

Subject the molten sodium chloride to an electric current

Next, we will subject the molten sodium chloride to an electric current by placing two electrodes (positive and negative) into the molten salt. The electric current will cause the ions (Na^+ and Cl^−) in the molten sodium chloride to move towards their respective electrodes.

Ion attraction to the electrodes

In this step, the positive sodium ions (Na^+) will be attracted to the negative electrode (cathode) and the negative chloride ions (Cl^−) will be attracted to the positive electrode (anode). This movement of ions is crucial for driving the chemical reactions that lead to the production of the elemental gas and sodium metal.

Chemical reactions at the electrodes

At the cathode (negative electrode), the sodium ions (Na^+) will gain electrons from the electrode and be reduced to form sodium metal (Na). The chemical reaction can be represented by the following equation: \[Na^+ + e^- \to Na\] At the anode (positive electrode), the chloride ions (Cl^−) will lose electrons to the electrode and be oxidized to form elemental chlorine gas (Cl_2). The chemical reaction can be represented by the following equation: \[2Cl^- \to Cl_2 + 2e^-\]

Collection of products

Finally, we will collect the products formed. Sodium metal will be formed at the cathode and can be collected as a solid, while chlorine gas produced at the anode can be collected and contained. Through this step-by-step process, we have demonstrated how electrolysis can be used to produce elemental chlorine gas and sodium metal from molten sodium chloride (table salt).

Key concepts

The Electrolysis Process

Electrolysis is a fascinating electrical process used to break down a compound into its elements by using electricity. Imagine it as a way to decompose chemical compounds with the power of electrons!

When it comes to the electrolysis of sodium chloride (NaCl), it generally involves melting the salt to create a molten state where its ions can roam free. This flexibility is crucial because, in a solid state, the ions are locked in place and not able to move freely. Think of it as freeing the ions from their crystal cage so that they can participate in the electrolysis 'party'.

Once the NaCl is molten, an electric current is introduced via electrodes plunged into this liquid. This electric input is the 'invitation' needed for the ions to begin their journey to the electrodes that match their electrical charge. Positive sodium ions (Na+) head towards the negative electrode (cathode), and negative chloride ions (Cl−) make their way over to the positive electrode (anode). This movement is essential because it's the ions reacting at the electrodes that create the magic—the chemical reactions that produce new substances, such as elemental gas and sodium metal in this case.

Chemical Reactions during Electrolysis

The true spectacle of electrolysis is the set of chemical reactions that occur at the electrodes. At the heart of these reactions are two fundamental processes: oxidation and reduction, known together as redox reactions.

At the negative electrode, or the cathode, reduction takes place. This is where the positively charged sodium ions (Na+) encounter free electrons (\textbf{e-}) provided by the electrode. The sodium ions grab these electrons in a chemical high-five to become neutral sodium atoms (\textbf{Na}). This reaction can be described with the simple but powerful equation: \[Na^+ + e^- \to Na\]

Meanwhile, at the positive electrode, the anode, oxidation occurs. Here, the negatively charged chloride ions (Cl−) are forced to give up their extra electrons, essentially getting 'oxidized', and they pair up to form diatomic chlorine gas (Cl_2), a process that can be succinctly captured by the equation: \[2Cl^- \to Cl_2 + 2e^-\]

After these reactions, the newly formed sodium metal and chlorine gas can be collected. The ability to produce such pure elemental substances from compounds demonstrates the practical applications of electrolysis in industrial chemistry.

Ions and Electrodes

Understanding the roles of ions and electrodes is key to grasping the electrolysis process. Ions are charged particles—sodium chloride in its molten state splits into sodium ions (Na+) and chloride ions (Cl−), each carrying a positive and negative charge respectively.

Electrodes serve as the 'hosts' for the electrolysis party: the cathode invites cations or positively charged ions, while the anode welcomes anions or negatively charged ions. They are not just inert bystanders but participate actively by giving electrons to cations or accepting electrons from anions. In our scenario with sodium chloride, the electrodes are where the transformative reactions happen. The cathode reduces the Na+ ions to Na atoms, while the anode oxidizes Cl− ions into Cl_2 gas.

The choice of electrode material can influence the efficiency and outcome of the electrolysis as well. Inert electrodes like graphite or platinum are often used because they do not react with the substances being produced. However, the selection depends on the specific electrolysis conditions and desired products.