Real-Life Applications of Limestone in Chemistry
Have you seen the Taj Mahal, one of the seven wonders of the world? If yes, then you must be amazed to see its majestic beauty, white colour and eternal testament to the artistic and scientific accomplishments of a wealthy empire. Do you know what the Taj Mahal is made of? If no, then the answer is Taj Mahal is made up of marble which is a mineral called Limestone. Not only the Taj Mahal but the outer covering of the Great Pyramid of Giza was also made up of Limestone. The Great Pyramid of Giza is also one of the seven wonders of the world. It must be understood that we have been using limestone for construction workk since ancient times. Before discussing its various uses, let's understand what limestone is and its various properties.
What is Limestone?
Limestone is an extensively versatile mineral. It is a carbonated sedimentary rock that is formed predominantly on the seafloor where materials rich in calcium carbonates accumulate. Its main component is calcium carbonate (CaCO3). This is the reason calcium carbonate is also called limestone. Marine organisms such as coral, foraminifera etc. leave their calcium carbonate shells behind when they die. About 10% of the sedimentary rocks are limestones.
Limestones are soluble in water and weak acids. It also contains variable amounts of silica in the form of chert. Limestone can be of yellow, white, or grey in colour.
Characteristics of Limestone
Few characteristics of limestone are listed below –
It almost always has some impurities, that is why it’s not perfectly white in color.
It is mainly formed by calcium carbonate shells of marine animals.
It is a part of the diet of terrestrial animals. It is added in the diet of poultry animals to improve egg quality.
It is mostly found in the shallow ends of marine water.
Chalk is a type of limestone.
It absorbs pollutants.
Limestone is able to form karst topography.
It reacts with hydrochloric acid and produces bubbles. This is the reason acid testing is considered one of the most reliable field tests for limestone.
When any type of limestone undergoes metamorphism, they recrystallize as marbles.
Uses of limestone
Limestone is one of the important resources for human beings. It is an extremely versatile mineral that is used in various fields and in numerous ways. We can easily find objects made up of one or another form in almost every common household. A few of its uses are listed below –
In building and decorative stones – Limestone has been used in construction since ancient times. Taj Mahal, the exquisite marble structure in Agra, India is an example of the usage of limestone in artistic accomplishments. Limestone is still being used in construction work in many ways. Its resistance to weather and aesthetic appeal makes it more suitable for this purpose.
Aggregates – Limestone is crushed and sorted into various sizes for its use for various purposes. It is one of the main components of concrete. It is coated with bitumen to make asphalt. Most of its aggregates are used in the formation of bases of roads, walls, paving slabs, decorative pieces etc.
Industrial purposes – Calcium carbonate is used in industries. It is used as a flux in steel making. It is also used for soil conditioning and latex treatment. It is the main ingredient of animal feed supplements (e.g. poultry grit).
Lime burning – It has been used for lime burning since the 1920s. Lime burning is also called calcining. When limestone is heated at high temperature, it breaks down into lime (calcium oxide) and carbon dioxide gas. Reaction if given below of decomposition of limestone or calcium carbonate –
Thus, it is a raw material for manufacturing quicklime.
Cement – Portland cement is a product of limestone which on mixing with aggregates makes concrete.
Agriculture – It is used as a soil conditioner. It is the main component of many fertilisers. It is used to neutralise acidic soils.
Petroleum reservoirs – Its geological formations are among the best petroleum reservoirs.
In pollution control – It reacts with sulphur dioxide so used in air pollution control as a reagent in flue – gas desulfurization.
In Glassmaking – Limestone is used in glassmaking.
As a source of calcium – It is used as a source of calcium and its purified form is added in breads and cereals.
In mining – It is used in the mining process as it can suppress methane explosions.
To increase the alkalinity of water – It is used to increase the alkalinity of water to prevent pipe corrosion.
In medicines – Calcium carbonate is used as a gastric antacid. It is also used as a phosphate binder for the treatment of hyperphosphatemia. It is also used as an inert filler for tablets.
In cosmetics – In many cosmetics products also it is used as filler.
In sculptures – It easily mixes with clay and due to its white colour, it is used in making sculptures. It gives them a bright white colour as well.
Great Pyramid of Giza – Great Pyramid of Giza is one of the seven wonders of the world. Its outside covering is entirely made up of limestone.
As raw material for synthesis – It is used as raw material for the synthesis of many chemicals such as slaked lime, quicklime and mortar etc.
The world's largest limestone quarry is at Michigan Limestone in Rogers City, Michigan. The Megalithic Temples of Malta are entirely composed of limestone. The white cliffs of Dover are also made up of limestone. Generally, spectacular rocky outcrops and islands are bands of limestone emerging from the Earth's surface long back. Thus, limestone is a very useful mineral for mankind.
This is all about Limestone, if you are looking for solutions to NCERT Textbook problems based on this topic, then log on to the Vedantu website or download Vedantu Learning App. By doing so, you will be able to access free PDFs of NCERT Solutions as well as Revision notes, Mock Tests and much more.
FAQs on Uses of Limestone Explained
1. What is limestone, and what is its primary chemical composition?
Limestone is a sedimentary rock composed mainly of calcium carbonate (CaCO₃). It often contains impurities such as clay, silt, and sand. It is formed over millions of years from the accumulation of shells, coral, and other marine organism debris on the seafloor. Its composition makes it a base, allowing it to react with and neutralise acids.
2. What are the top 5 most common uses of limestone?
Limestone is an extremely versatile material with numerous applications. The top five uses are:
- Construction: Used as a building material, in road construction, and as a key ingredient in cement.
- Agriculture: To neutralise acidic soil and improve crop yield, a process known as liming.
- Manufacturing: A crucial raw material in the production of iron, steel, glass, and paper.
- Chemicals: Used to produce quicklime (calcium oxide) and slaked lime (calcium hydroxide).
- Environmental: For flue-gas desulfurisation to remove pollutants from industrial emissions and for water purification.
3. How is limestone used in agriculture to improve soil quality?
Limestone is used in agriculture primarily to treat acidic soils. When soil becomes too acidic, it can lock up essential nutrients and increase the toxicity of elements like aluminium, hindering plant growth. Adding crushed limestone (agricultural lime) raises the soil's pH, a process called liming. This neutralisation makes nutrients like phosphorus and potassium more available to plants and improves the overall soil structure for better water retention and root growth.
4. What makes limestone a preferred material for construction and architecture?
Limestone is favoured in construction for several key reasons. It is a durable and weather-resistant material, allowing buildings to last for centuries. Aesthetically, it has a natural, classic appeal and is relatively easy to cut and carve into blocks and decorative shapes. Furthermore, it is a primary raw material in the manufacturing of cement, which is the binding agent in concrete, the most widely used construction material globally.
5. What is the chemical process for converting limestone into quicklime and slaked lime?
The conversion involves two main steps. First, limestone (CaCO₃) is heated to about 900°C in a kiln. This process, known as calcination, causes it to decompose into quicklime (calcium oxide, CaO) and carbon dioxide gas (CO₂).
CaCO₃ (s) → CaO (s) + CO₂ (g)
Next, quicklime is converted to slaked lime (calcium hydroxide, Ca(OH)₂) by adding water in a highly exothermic reaction called slaking.
CaO (s) + H₂O (l) → Ca(OH)₂ (aq)
6. How does limestone differ from other carbonate rocks like chalk and marble?
While limestone, chalk, and marble are all primarily composed of calcium carbonate, they differ in their formation and structure.
- Limestone is a sedimentary rock formed from marine debris.
- Chalk is a softer, more porous form of limestone, composed of microscopic fossil shells of coccolithophores.
- Marble is a metamorphic rock. It forms when limestone is subjected to intense heat and pressure, causing the calcite crystals to recrystallise and interlock, resulting in a harder, denser, and often beautifully veined stone.
7. What specific role does limestone play in the manufacturing of steel?
In steel manufacturing, limestone acts as a flux in the blast furnace. When heated, it decomposes into calcium oxide (quicklime). This calcium oxide then reacts with impurities in the iron ore, such as silica (sand), to form a molten slag (calcium silicate). This slag is less dense than the molten iron and floats on top, allowing it to be easily separated, thus purifying the iron which is then processed into steel.
8. How can limestone be used to reduce environmental pollution?
Limestone plays a significant role in controlling pollution. In a process called flue-gas desulfurisation, powdered limestone is used to remove sulphur dioxide (a major cause of acid rain) from the emissions of power plants. The calcium carbonate reacts with the sulphur dioxide to form calcium sulphite, which can then be removed. It is also used to neutralise acidic water in lakes and streams affected by acid rain.
9. Can limestone be used in its raw form for most applications?
No, limestone often requires processing. For construction, it is crushed into aggregate or cut into blocks. For agriculture, it is pulverised into a fine powder to react more effectively with the soil. For chemical and industrial uses, such as in steel or cement manufacturing, it must be heated in a kiln (calcined) to be converted into calcium oxide (quicklime), which is far more reactive than its original carbonate form.
10. What are the main physical characteristics used to identify limestone?
Key physical characteristics for identifying limestone include its relatively soft texture (it can be scratched with a steel knife), its granular appearance, and its colour, which is typically white, grey, or tan. The most definitive test is the acid test: placing a drop of a weak acid, like vinegar or dilute hydrochloric acid, on the rock will cause it to bubble or fizz as the calcium carbonate reacts to release carbon dioxide gas.
