The formula of carnallite is:

Carnallite, also known as potassium magnesium chloride, is a hydrated evaporite mineral with the chemical formula: KMgCl3 ⋅ 6H2O.

It consists of:

• Potassium chloride (KCl)
• Magnesium chloride (MgCl₂)
• Six water molecules (6H₂O)

Properties of Carnallite:

• Appearance: Carnallite can appear in various colors, including yellow, white, reddish, colorless, or even blue.
• Nature: It is a naturally occurring evaporite mineral that forms in arid environments where seawater has evaporated.

Explanation of the Correct Answer:

The carnallite formula shows the combination of potassium, magnesium, chloride ions, and water molecules in a specific hydrated structure.

- The presence of water of crystallization makes it a hydrated salt.

- This unique composition is why carnallite is used as a source for magnesium and potassium in industrial applications.

Correct Option: (b) KCl ⋅ MgCl₂ ⋅ 6H₂O

Why This Answer Is Correct?

- The chemical formula KCl ⋅ MgCl2 ⋅ 6H2O represents the exact structure of carnallite.

- Other options do not include both magnesium chloride and water molecules, which are essential parts of the carnallite formula.

Key Takeaways

• Carnallite Formula: KCl ⋅ MgCl2 ⋅ 6H2O
• Composition: Contains potassium chloride, magnesium chloride, and water molecules.
• Uses: It is a source of magnesium and potassium, commonly found in evaporite deposits.

The correct answer is option b because it accurately represents the composition of carnallite.