Problem 167 - A Complete Resource Book in Chemistry for JEE Main

Question

The substance not likely to contain \(\mathrm{CaCO}_{3}\) is [2003] (a) sea shells (b) calcined gypsum (c) dolomite (d) a marble statue

Step-by-Step Solution

Answer

Calcined gypsum is the substance not likely to contain 2\mathrm{CaCO}_{3}2.

Step 1: Understanding Calcium Carbonate

Calcium carbonate (2 extrm{CaCO}_32) is a common substance found in rocks as the minerals calcite and aragonite. It is the main component of shells of marine organisms, snails, pearls, and eggshells. It is often used in the construction industry in the form of limestone and marble.

Step 2: Analyzing Sea Shells

Sea shells are primarily composed of calcium carbonate. Therefore, they are a natural part of organisms like snails, oysters, and corals, making sea shells a source of 2 extrm{CaCO}_32.

Step 3: Analyzing Calcined Gypsum

Calcined gypsum, or plaster of Paris, is produced by heating gypsum (2 extrm{CaSO}_4 2 extrm{.2H}_2 extrm{O}2). It does not involve calcium carbonate in its composition or production process, as it primarily contains calcium sulfate.

Step 4: Analyzing Dolomite

Dolomite is a mineral that contains calcium magnesium carbonate, 2 extrm{CaMg(CO}_3)_22. It is indeed related to calcium carbonate, having a carbonate group as part of its structure.

Step 5: Analyzing a Marble Statue

Marble is a metamorphic rock composed mostly of recrystallized carbonate minerals, primarily calcite, which is a form of calcium carbonate. Thus, marble statues are very likely to contain 2 extrm{CaCO}_32.

Step 6: Conclusion

Upon careful analysis of all options, calcined gypsum is identified as the substance least likely to contain calcium carbonate, as it is primarily composed of calcium sulfate.

Key Concepts

Minerals

Minerals are naturally occurring substances with a defined chemical composition and crystalline structure. They are the foundation of rocks and are crucial to understanding geology and Earth's materials. Calcium carbonate (\( \text{CaCO}_3 \)) is one of the most abundant minerals, commonly found as calcite and aragonite. Aragonite is primarily found in mollusk shells and the pearls of marine life.
Calcite is another form that often occurs in sedimentary rocks like limestone, and is a major component in biological structures such as eggshells. The diversity of minerals is vast, with each having unique properties that determine their practical uses. For example, calcium carbonate not only plays a significant role in nature but is also utilized in various industrial applications due to its chemical stability and abundance.

Construction Materials

Construction materials are essential for building and infrastructure projects. They are selected based on properties like strength, durability, and availability. Calcium carbonate is particularly important in the construction industry.
Limestone and marble, both rich in calcium carbonate, are prized for their strength and aesthetic appeal. Limestone is commonly used for road bases, as aggregate for concrete, and in cement manufacturing.
Marble stands out for its decorative value and is commonly used in sculptures and high-end flooring due to its elegance and smooth surface. In construction, it's crucial to use materials that match the functionality and environment of the project, and calcium carbonate-based materials offer both versatility and cost-effectiveness.

Chemical Composition

The chemical composition of a substance defines its identity and properties. Calcium carbonate (\( \text{CaCO}_3 \)) is a compound made up of calcium (\( \text{Ca} \)), carbon (\( \text{C} \)), and oxygen (\( \text{O}_3 \)). This composition grants it specific characteristics such as basicity, solubility in water, and reaction with acids.
In naturally occurring forms, it appears in various mineralogical forms such as calcite and aragonite. Each form, though chemically identical, exhibits different physical characteristics due to distinct crystal structures. This illustrates how the same chemical formula can give rise to diverse physical materials. Consequently, understanding the chemical composition is key to leveraging the properties of materials for practical applications, particularly in sciences and engineering.

Marble

Marble is a metamorphic rock known for its beauty and strength, commonly composed of recrystallized carbonate minerals, mainly calcite, which contains calcium carbonate (\( \text{CaCO}_3 \)). It results from the transformation of limestone under intense heat and pressure conditions deep within the Earth.
This process realigns the calcite crystals, giving marble its characteristic shine and extensive range of colors and patterns, which depend on the impurity levels and mineral content during its formation. Due to its aesthetic qualities, marble is highly sought after for artistic purposes, such as sculptures and architectural features like columns and tiles.
Aside from aesthetics, marble's durability makes it a preferred material in construction, ensuring it remains a prominent choice for both builders and artists.