Question

Carnallite on electrolysis gives: (a) \(\mathrm{Na}\) and \(\mathrm{CO}_{2}\) (b) \(\mathrm{Mg}\) and \(\mathrm{Cl}_{2}\) (c) \(\mathrm{Al}\) and \(\mathrm{Cl}_{2}\) (d) \(\mathrm{Ca}\) and \(\mathrm{Cl}_{2}\)

Short answer

Option (b) \( \text{Mg} \) and \( \text{Cl}_2 \).

Step-by-step solution

Identify the Components of Carnallite

Carnallite is a mineral composed primarily of hydrated potassium magnesium chloride, with the chemical formula \( \text{KMgCl}_3 \cdot 6\text{H}_2\text{O} \). It is a double chloride of potassium and magnesium, hence contains \( \text{K}^+ \), \( \text{Mg}^{2+} \), and \( \text{Cl}^- \) ions.

Electrolysis Process Introduction

In electrolysis, electricity is used to drive a non-spontaneous chemical reaction. When molten carnallite is subjected to electrolysis, it breaks down into its constituent elements: magnesium (from \( \text{Mg}^{2+} \) ions) and chlorine gas (from \( \text{Cl}^- \) ions). Potassium ions may also be present but typically are not reduced under normal conditions due to higher electrode potential needs.

Predict the Electrolysis Products

Based on the components of carnallite, during electrolysis, \( \text{Mg}^{2+} \) ions gain electrons (reduced) to form magnesium metal \( \text{Mg} \), and \( \text{Cl}^- \) ions lose electrons (oxidized) to form chlorine gas \( \text{Cl}_2 \). Thus, the main products are \( \text{Mg} \) and \( \text{Cl}_2 \).

Match Answer to Options

From the provided options, the one that matches the predicted products of electrolysis of carnallite, \( \text{Mg} \) and \( \text{Cl}_2 \), is option (b), which states \( \text{Mg} \) and \( \text{Cl}_2 \).

Key concepts

Carnallite

Carnallite is a fascinating mineral that plays a crucial role in the extraction of magnesium and chlorine gas through the process of electrolysis. It is primarily composed of hydrated potassium magnesium chloride, which is expressed chemically as \( \text{KMgCl}_3 \cdot 6\text{H}_2\text{O} \). This means that each molecule of carnallite consists of one potassium ion (\( \text{K}^+ \)), one magnesium ion (\( \text{Mg}^{2+} \)), and multiple chloride ions (\( \text{Cl}^- \)), along with water molecules.
In terms of its physical appearance, carnallite often appears as a colorless or white crystal that might contain a hint of a pink or yellow tone, depending on impurities present. It is an important raw material for the production of potash, which is used in fertilizers.

• Its natural occurrence is in evaporite deposits, which are essential for harvesting these valuable ions.
• Carnallite's structure with its water of crystallization is an interesting aspect in its formation and breakdown.

Understanding the nature of carnallite is fundamental when delving into how electrolysis transforms this mineral into valuable elements like magnesium metal and chlorine gas.

Magnesium

Discovering the secret of magnesium is essential in understanding electrolysis involving carnallite. During electrolysis, the \( \text{Mg}^{2+} \) ions present in carnallite gain electrons in a process known as reduction. This reduction results in the creation of magnesium metal (\( \text{Mg} \)).
Magnesium is a lightweight, silvery-white metal that has excellent properties for use in various industries. It is valued for its:

• Low density, which makes it ideal for lightweight structural materials.
• High strength-to-weight ratio.
• Resistance to corrosion, which makes it a great component in alloys and in the automotive industry.

The production of magnesium from carnallite through electrolysis is significant for industries focusing on recycling, aerospace, and automobile manufacturing due to its versatile properties and abundant availability.
Keep in mind that magnesium plays a vital role not just industrially but biologically as well, being an essential element in human health, assisting in over 300 enzyme reactions in the body.

Chlorine Gas

Chlorine gas is one of the crucial products obtained through the electrolysis of carnallite. When \( \text{Cl}^- \) ions from carnallite are subjected to electrolysis, they undergo oxidation by losing electrons, forming chlorine gas \( \text{Cl}_2 \).
Chlorine gas is a greenish-yellow gas at room temperature and possesses a distinctive pungent odor. It is essential due to its:

• Use in water disinfection to purify drinking water and in swimming pool maintenance.
• Role as a raw material in the production of numerous chemicals.
• Function in creating polyvinyl chloride (PVC) and other plastics.

Despite its numerous uses, chlorine gas must be handled with caution due to its potentially harmful effects on health if inhaled. Its production via electrolysis of carnallite underscores the importance of safe and controlled industrial procedures in chemical manufacturing.
By understanding the applications and properties of chlorine gas, one can fully appreciate its vital functions in our daily lives and industries.