Question

What products are obtained in the electrolysis of molten NaI?

Short answer

The products obtained in the electrolysis of molten NaI are iodine (\(I_2\right)\right) at the anode and sodium metal (Na) at the cathode.

Step-by-step solution

Understanding Electrolysis Process

Electrolysis is the process where an electric current is passed through a substance to effect a chemical change. In this case, the substance is molten NaI (sodium iodide), which will decompose into its constituent elements.

Identifying the Anode and Cathode Reactions

In the molten state, NaI dissociates into Na+ (sodium ions) and I- (iodide ions). At the anode, an oxidation reaction occurs where negative ions (anions) lose electrons. At the cathode, a reduction reaction takes place where positive ions (cations) gain electrons.

Writing the Half Reactions at the Anode

At the anode, iodide ions are oxidized to iodine. The half reaction for this process is: \(2I^- - 2e^- \rightarrow I_2\).

Writing the Half Reactions at the Cathode

At the cathode, sodium ions are reduced to sodium metal. The half reaction for this process is: \(Na^+ + e^- \rightarrow Na\).

Listing the Products of Electrolysis

From the half reactions, the products of the electrolysis of molten NaI are iodine (\(I_2\)) at the anode and sodium metal (Na) at the cathode.

Key concepts

Electrolysis Process

Electrolysis is a fascinating and widely-used chemical process where electrical energy is used to drive a non-spontaneous chemical reaction. This process is crucial in many industrial applications, where it's employed to extract metals from their ores, produce gases, or deposit coatings on materials. Think of electrolysis as a way to 'split' a compound into its elemental components using an electric current.

When it comes to the electrolysis of molten sodium iodide (NaI), we introduce two electrodes into liquid NaI and apply an electrical current. Because NaI is an ionic compound, it consists of positively charged sodium ions (\( Na^+ \)) and negatively charged iodide ions (\( I^- \)), which move towards the electrodes where they are converted into neutral atoms through reactions at the surface of the electrodes.

Anode and Cathode Reactions

Within the electrolytic cell, two types of reactions occur at two different electrodes: oxidation at the anode and reduction at the cathode. To remember which is which, an anode is where anions (negative ions) go, and it's where oxidation happens – it’s an 'ANOX' reaction. Conversely, a cathode is where cations (positive ions) go, and reduction occurs – a 'CathRed' reaction.

Here's a simpler way to see it:

• The anode attracts anions because it is positively charged, and here the ions lose their electrons (oxidation).
• The cathode, negatively charged, pulls in cations, which gain electrons to form neutral atoms (reduction).

For the NaI electrolysis, at the anode, iodide ions relinquish electrons, while at the cathode, sodium ions pick up electrons.

Oxidation and Reduction

Understanding oxidation and reduction is critical to mastering the basics of chemistry, especially when discussing electrolysis. At its core, oxidation is the process of losing electrons, while reduction is the process of gaining electrons. Remember the acronym OIL RIG - 'Oxidation Is Loss, Reduction Is Gain.' These two processes occur simultaneously in any redox reaction, including the reactions at the anode and cathode during electrolysis.

In our example of molten NaI, the iodide ions (I-) are oxidized to iodine (I2) when they lose their electrons. On the flip side, sodium ions (Na+) are reduced to sodium metal (Na) when they gain electrons. You can envision electrons as the currency of the chemical world, where they are transferred from one species (oxidized) to another (reduced).

Half Reactions

Half-reactions are a way to break down the overall redox reaction into two simpler parts, which show the oxidation and reduction processes separately. Each half-reaction displays the movement of electrons and the change in charge of the ions involved. The brilliance of half-reactions lies in their ability to detail the precise nature of the electron transfer during a reaction.

For electrolysis of molten NaI, the half-reactions tell the full story:

• At the anode: Oxidation of iodide ions - \(2I^- \rightarrow I_2 + 2e^-\)
• At the cathode: Reduction of sodium ions - \(Na^+ + e^- \rightarrow Na\)

By analyzing these half-reactions, students can understand the change each reactant undergoes and the stoichiometry of the electrons involved, thereby predicting the products of electrolysis.