Question

Compare the chemical formula of magnetite with that of biotite. Why is magnetite mined to obtain iron supplies, but biotite is not?

Short answer

The chemical formula of magnetite is \(Fe_3O_4\), while biotite is \(K(Mg,Fe)_3[AlSi_3O_{10}](OH)_2\). Magnetite is primarily composed of iron and oxygen, while biotite is a complex silicate with lesser iron content. Magnetite is mined for iron supplies due to its higher iron percentage and simpler, cost-effective extraction process. In contrast, biotite is not preferred for iron extraction due to its lower iron content and complex extraction process.

Step-by-step solution

Write the chemical formula of magnetite and biotite

Magnetite has a chemical formula of: \[Fe_3O_4\] Biotite has a chemical formula of: \(K(Mg,Fe)_3[AlSi_3O_{10}](OH)_2\)

Compare the chemical compositions of the two minerals

When we compare the chemical formulas of magnetite and biotite: - Magnetite is an iron oxide, containing iron and oxygen atoms in its structure. - Biotite, on the other hand, is a complex silicate, containing potassium, magnesium, iron, aluminum, silicon, and hydroxyl groups in its structure.

Analyze why magnetite is preferred for obtaining iron supplies but not biotite

Magnetite is the mineral that is preferred for obtaining iron supplies because: 1. It has a higher percentage of iron in its structure (\(Fe_3O_4\) means it has three iron atoms per molecule). 2. The extraction process of iron from magnetite is simpler and less expensive as it involves reducing the iron oxide with carbon, usually in a blast furnace, to obtain iron metal. Biotite, on the other hand, is not preferred for obtaining iron supplies because: 1. It has a lower percentage of iron in its structure (only 1-3 iron atoms in a complex silicate molecule). 2. The extraction process of iron from biotite is more complex and involves various chemical reactions, which makes it more expensive and less attractive for obtaining iron supplies. In conclusion, magnetite is mined for obtaining iron supplies because it has a higher percentage of iron in its structure, and its extraction process is simpler and more cost-effective, compared to biotite.

Key concepts

Magnetite

Magnetite is a naturally occurring mineral with the chemical formula \(Fe_3O_4\). This means that in each molecule of magnetite, there are three iron (Fe) atoms and four oxygen (O) atoms. Magnetite is an iron oxide, and its significant iron content makes it one of the primary ores for iron extraction.

A unique property of magnetite is its magnetic nature, which is why it's named so. It can be easily visualized as a black or brownish-black mineral with a distinct metallic sheen.

- High iron content: Magnetite's chemical structure, being composed significantly of iron, allows it to serve as a major source of iron ore.- Simplicity in extraction: The process of obtaining iron from magnetite is straightforward and involves heating the mineral with carbon, which reduces the iron oxide to molten iron metal.

Considering these characteristics, magnetite is extensively mined and plays a crucial role in steel production.

Biotite

Biotite is a type of mica, known for its sheet-like crystal structure and its chemical complexity. Its chemical formula is \(K(Mg,Fe)_3[AlSi_3O_{10}](OH)_2\). In this formula:

• K represents potassium
• \((Mg,Fe)_3\) indicates that magnesium and iron can substitute for each other in three places within one molecule.
• \([AlSi_3O_{10}]\) denotes a complex silicate structure composed of aluminum, silicon, and oxygen.
• \((OH)_2\) means that hydroxide groups are also part of the structure.

Biotite's structure is far more complex than that of magnetite. While biotite does contain iron, it is only a part of a much larger and more complicated crystalline structure. This results in biotite having only a minor iron content relative to its total molecular composition. Hence:
- Lower iron content: Compared to magnetite, the presence of iron in biotite is minimal.- Extraction complexity: The process of extracting iron from biotite would require breaking down a complex silicate structure, making it inefficient and costly.
Therefore, due to its low iron content and extraction challenges, biotite is not mined for iron.

Iron Extraction

Iron extraction from iron ores like magnetite involves several steps that primarily aim to separate iron from other elements present in the ore. It's a crucial industrial process integral to steel production.

- **Primary method**: The main method of extracting iron from magnetite involves a reduction process in a blast furnace. Here, magnetite is mixed with coke (a form of carbon) and subjected to high temperatures.- **Chemical reaction**: In the blast furnace, the carbon in coke reacts with the oxygen in the iron oxide (\(Fe_3O_4\)) to form carbon dioxide and pure iron.- **Result**: This results in a molten iron that can be further refined and used to create various iron and steel products.

The overall iron extraction process is efficient and cost-effective for ores with high iron content like magnetite, unlike more complex silicates such as biotite. Therefore, the choice of the source mineral is critical in determining the feasibility and efficiency of iron production.