Calcium Carbonate and Calcium Sulphate(Plaster of Paris)

Introduction

Imagine a world with no concrete structures, flowing fresh water, or any of the exquisite artworks. These seemingly very basic utilities all find their root in common, yet imperative, chemical compounds. Among the myriad vital roles that these compounds have played, the most striking have been those for Calcium Carbonate and Calcium Sulfate. Be it the limestone forming its very foundation, the chalk that aids us in our educational pursuits, or the hard, detailed plaster of Paris casts that seem to immortalize art, these appear as precious compounds.

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This Story also Contains

1. Introduction
2. Understanding Calcium Carbonate and Calcium Sulphate
3. Calcium Carbonate and Calcium Sulphate Types and Features
4. Some Solved Examples
5. Summary

A reagent is used in these great scales: from classical application in spectacular limestone cliffs and marble statues to fine powder dusted in classrooms. Other uses of it include its application within industries as well as its effects on healthcare. Calcium Sulphate, particularly Plaster of Paris, gained a name when it comes to applications that would require setting fast; in addition to architectural and artistic restorations, there are also construction as well as exposition medical applications. One of its bizarre properties is that after having been a mold for artistic or architectural restoration, the Plaster of Paris gets shaped and then can be set fast to make it into a solid mold.

The second page describes to the reader the world of calcium carbonate and calcium sulphate by defining the properties and applications of their compounds in the most diverse areas. First, a presentation of those two major concepts will be made to bring out a solid base on their chemical nature and importance. The types and forms the compounds take can then bring out the distinct uses and benefits. Finally, practical applications with a special focus on how they have impacted our lives and our industries shall be presented. By the end of it all, you will have acquired an overview of these important compound groups and their numerous functions in our universe.

Understanding Calcium Carbonate and Calcium Sulphate

Definitions and Explanations

Calcium carbonate, CaCO₃ is obtained in most rocks, primarily as the minerals calcite and aragonite. It forms the principal constituents of pearls, shells of marine organisms, and eggshells. Calcium sulphate, CaSO₄ occurs in a number of hydrated forms; the most well-known are gypsum, CaSO₄·2H₂O, and plaster of Paris, CaSO₄·0.5H₂O. Gypsum is converted to plaster of Paris on heating at about 150°C when it loses three-quarters of its water. Both find applications in various industrial and biological fields whereby their chemical composition and formation are core to their other applications more significantly.

Calcium Carbonate, CaCO3
In nature, it occurs as limestone, ice land spar, marble, and shells of sea animals.

Preparation
In the laboratory, it is prepared by passing CO₂ through lime water or by adding sodium carbonate solution into calcium chloride as follows:

$\begin{aligned} & \mathrm{Ca}(\mathrm{OH})_2+\mathrm{CO}_2 \rightarrow \mathrm{CaCO}_3+\mathrm{H}_2 \mathrm{O} \\ & \mathrm{CaCl}_2+\mathrm{Na}_2 \mathrm{CO}_3 \longrightarrow \mathrm{CaCO}_3+2 \mathrm{NaCl}\end{aligned}$

Uses

• It is used in the preparation of cement, and washing soda (NaHCO₃ by Solvay method).
• In the extraction of many metals like iron.
• Marble is used as a building material.
• Precipitated chalk is used in the manufacture of paints, medicines toothpaste, etc.

Calcium Sulphate (Plaster of Paris), CaSO4·1⁄2 H2O
It is known as calcium sulphate hemihydrate

Preparation
It is obtained when gypsum, CaSO_4.2H₂O, is heated to 393 K.

$2\left(\mathrm{CaSO}_4 \cdot 2 \mathrm{H}_2 \mathrm{O}\right) \rightarrow 2\left(\mathrm{CaSO}_4\right) \cdot \mathrm{H}_2 \mathrm{O}+3 \mathrm{H}_2 \mathrm{O}$

Above 393 K, no water of crystallization is left and anhydrous calcium sulphate, CaSO₄ is formed. This is known as ‘dead burnt plaster’. It has a remarkable property of setting with water. On mixing with an adequate quantity of water it forms a plastic mass that gets into a hard solid in 5 to 15 minutes.

Uses

• Plaster of Paris is used for plaster of broken bones, making statues, toys, chalks, etc.
• It is also used as a building material.
• It is used for making molds for casting.

Calcium Carbonate and Calcium Sulphate Types and Features

Types and Implication

Calcium carbonate primarily occurs in three types: calcite, aragonite, and vaterite. Calcite is very stable and common; it represents limestone and marble. Aragonite formed through seawater while vaterite represents fewer conditions and it's not very stable. Calcium sulphite is available in forms such as gypsum and anhydrite CaSO₄ without water. Gypsum finds huge applications in buildings mainly in drywall but Plaster of Paris is used in casts, molds, and sculpture. Each form has unique properties and uses hence it clearly shows how modest these compounds are in different aspects.

Real-Life Relevance and Applications

Real-Life Applications

Calcium carbonate plays a very significant role in construction due to its inclusion in cement and concrete. It also acts as a dietary calcium supplement and an antacid. In the paper industry, it is used as a filler and coating material. This application provides more enhanced quality to the paper. Calcium sulphate, especially in the form of Plaster of Paris, is very important to medicine in making casts and splints. It can be used in the arts in detailing small sculptures or molds. The uses relating to the environment are equally significant; the use of gypsum assumes the function of improving the structure and fertility of the soil. From a more scholastic view, knowledge about these compounds assists the learning process associated with geological formations, industrial processes, and biological functions.

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Some Solved Examples

Example 1

Question:

Which of the following options is true regarding the use of plaster of Paris?

1. It can be used in the building industry
2. Used in dentistry
3. Can be used for the immobility of the area of a fractured bone
4. All of these

Solution:

Plaster of Paris is widely used in various fields:

• It is used in the building industry for creating decorative elements.
• It is used in dentistry for making dental casts.
• It is used for immobilizing fractured bones by creating casts around the injured area.

Hence, the answer is option (4).

Example 2

Question:

Which of the following contains CaCO₃?

1. Chalk
2. Limestone
3. Marble
4. All of these

Solution:

Calcium Carbonate (CaCO₃) is found in all the given substances:

• Chalk is a form of CaCO₃.
• Limestone is primarily composed of CaCO₃.
• Marble is a metamorphic rock that also contains CaCO₃.

Hence, the answer is option (4).

Example 3

Question:

When CO₂ is passed through X, the solution turns milky white due to the formation of CaCO₃. What is X?

1. Ca(OH)₂
2. CaCO₃
3. CaO
4. None of these

Solution:

When CO₂ is passed through Ca(OH)2 (lime water), a milky white precipitate of CaCO₃ is formed as per the reaction:

Ca(OH)₂+CO₂→CaCO₃+H₂O

Hence, the answer is option (1).

Summary

Calcium carbonate and calcium sulphate represent those chemical compounds, which much more than existence, help at many levels in daily life and industries. From buildings and road construction to the execution of fine arts or devices used for medical purposes, they have a lot to do with everything. Thus, one who can know their properties, types, and uses enhances his respect toward such substances and, at the same time, points to the value of these materials as they are related to practical and academic aspects.