Problem 38 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following ore contains both calcium and magnesium? (a) lime stone (b) dolomite (c) epsom salt (d) carnalite

Step-by-Step Solution

Answer

The ore that contains both calcium and magnesium is dolomite.

Step 1: Identify Elements in Lime Stone

Lime stone is primarily composed of calcium carbonate, which contains calcium but not magnesium. Therefore, lime stone contains calcium but lacks magnesium.

Step 2: Analyze Dolomite Composition

Dolomite is a mineral composed of calcium magnesium carbonate, \[ \text{CaMg(CO}_3\text{)}_2 \]. This compound includes both calcium and magnesium atoms.

Step 3: Inspect Epsom Salt

Epsom salt, chemically known as magnesium sulfate heptahydrate, \[ \text{MgSO}_4 \cdot 7\text{H}_2\text{O} \], contains magnesium, but it does not contain calcium.

Step 4: Examine Carnalite Composition

Carnalite is known chemically as potassium magnesium chloride, \[ \text{KMgCl}_3 \cdot 6\text{H}_2\text{O} \]. Although it contains magnesium, it lacks calcium.

Step 5: Conclusion

After examining each option, the only mineral that contains both calcium and magnesium is dolomite.

Key Concepts

Ore Composition

Ore composition is the analysis of the elements and minerals present within an ore. An ore is naturally occurring and contains a mineral, or minerals, that can be mined for profit. To determine the composition of an ore, scientists and geologists perform tests to identify the key components.
These components could be metals such as calcium, magnesium, iron, or more.

Understanding the composition of an ore is crucial in the mining industry because it helps determine the feasibility of mining a particular ore.

• An ore with a high percentage of a valuable metal may be more economically viable to mine.
• Different elements in an ore may have different properties, such as melting points, affecting how they are extracted.

In this context, the main ores of interest are those that contain either calcium, magnesium, or both. Identifying these components helps in determining the further utility and value of the ore.

Mineral Identification

Mineral identification is the process of analyzing the physical and chemical properties of a mineral to determine its name and classification. This process often starts with observing the mineral's physical properties, like color, luster, hardness, and cleavage.

Chemical tests further aid in identification by showing what elements or compounds are in the mineral.

• For example, dolomite is identified due to its distinctive reaction with dilute hydrochloric acid, which produces a weak effervescence.
• The presence of both calcium and magnesium in dolomite gives it unique properties compared to minerals containing only calcium or only magnesium.

This comprehensive identification process ensures that each mineral is correctly categorized, making it easier to understand how it can be used or valued in various industries.

Chemical Formulas

Chemical formulas represent the composition of molecules and compounds using element symbols and numbers.
These formulas play a vital role in defining the exact structure and composition of chemical compounds.

For example, the chemical formula of dolomite is \( \text{CaMg(CO}_3\text{)}_2 \), indicating it contains both calcium (Ca) and magnesium (Mg) along with carbonate groups (\( \text{CO}_3 \)).

• This formula helps visualize the compound's structure and aids in calculating molecular weight or determining reactions.
• Understanding chemical formulas is essential for chemists and geologists when trying to deduce a mineral's properties or reactivity.

By using formulas, we achieve a precise method to convey complex chemical data simply and concisely, making it accessible for further academic or industrial applications.

Calcium Magnesium Carbonate

Calcium magnesium carbonate is the chemical name for the mineral dolomite.
It is noteworthy due to its dual composition involving both calcium and magnesium.

This mineral is primarily found as a gray or white crystal and is a significant source of magnesium and calcium for various industrial uses. Dolomite's properties are fascinating:

• It can be used for pH buffering in agricultural settings.
• It has applications in the production of glass and ceramics, where calcium magnesium carbonate helps to enhance product stability.
• It's used in construction and as a concrete aggregate due to its durability.

Such versatile applications are why understanding the chemical structure and composition of minerals like dolomite is crucial in many technological and industrial fields.