Element Elements and Compounds Compounds of Calcium Structure of Atom Compounds A compound is a...

ElementElements and Compounds Compounds of CalciumStructure of Atom

Compounds

A compound is a substance composed of two or more elements, chemically combined with one another in a fixed proportion.

Water, sugar, salt, carbon dioxide, methane etc are the examples of compounds.

Objectives:

Preparation, properties and Uses of Calcium oxide, Calcium hydroxide, Calcium carbonate, Plaster of Paris and Cement.

The s-Block Elements

ElementElements and Compounds Extraction of SulphurNon-metals

Compounds



Mineral Coal and Mineral Oil PetroleumThe s-Block Elements

Calcium oxide (CaO)

Calcium oxide is usually made by the thermal decomposition of limestone in a lime kiln.

Diagonal Relationship and IrregularityLithium and SodiumCompounds of Calcium

As soon as carbon dioxide is produced it is removed, so that the reaction goes towards completion (forward direction) and reverse reaction is stopped.


Compounds



Mineral Coal and Mineral Oil PetroleumStructure of AtomThe s-Block Elements

Lime is a white amorphous solid.

It has a high melting point of 2600oC.

It is highly stable and even fusion cannot decompose it.

Lithium and SodiumCompounds of Calcium

On hydration, quick lime forms slaked lime or lime water. When water is added to lime it becomes hot and cracks to form a white powder. This is called slaking of lime.

Properties


Compounds



Mineral Coal and Mineral Oil PetroleumStructure of Atom

Calcium oxide is a basic oxide. It can react with acids to give calcium salts.

The s-Block Elements Lithium and SodiumCompounds of Calcium

Properties

With acidic oxides like silicon dioxide and phosphorus pentoxide, it forms silicates and phosphates. This property makes lime useful as a flux in metallurgy to remove impurities.


Compounds




Uses

The s-Block Elements Lithium and SodiumCompounds of Calcium

Lime is indispensable for use with mortar and plaster.

It is used as a reagent in the manufacture of paper, high grade steel and cement.

It finds enormous use in the manufacture of soap, rubber, varnish and lime bricks.

Lime is used for medicinal purposes and insecticides.


Compounds




It has many names including hydrated lime, builders' lime, slack lime, cal, or pickling lime.

The s-Block Elements

Calcium hydroxide (Ca(OH)2)


In the laboratory it can be prepared by mixing an aqueous solutions of calcium chloride and sodium hydroxide.

Calcium hydroxide is produced commercially by treating lime with water.

CaO + H2O → Ca(OH)2

Calcium hydroxide, traditionally called slaked lime, is an inorganic compound with the chemical formula Ca(OH)2.


Compounds




Properties


It is a colourless crystal or white powder. It is sparingly soluble in water.

When heated to 512 °C, it decomposes into calcium oxide and water.

A suspension of fine calcium hydroxide particles in water is called milk of lime. The solution is called limewater and is a medium strength base that reacts with acids and attacks many metals.

Limewater turns milky in the presence of carbon dioxide due to formation of calcium carbonate.

Ca(OH)2 → CaO + H2O

Ca(OH)2 + CO2 → CaCO3 + H2O


Compounds




Uses


Sodium hydroxide is used in the preparation of mortar which is one of the components of building materials

It is used in white washing of walls because of its insecticide nature.

It is used in the purification of sugar and preparation of bleaching powder.

It is also used as antiseptic.


Compounds




Calcium carbonate (CaCO3)


Calcium carbonate, also known as limestone is a common substance found in rocks in all parts of the world, and is the main component of shells of marine organisms, snails, coal balls, pearls, and eggshells. It is usually the principal cause of hard water.

Calcium carbonate is prepared from calcium oxide. Water is added to calcium oxide which gives calcium hydroxide. Carbon dioxide is passed through this solution to precipitate the desired calcium carbonate.

CaCO3 → CaO + CO2 CaO + H2O → Ca(OH)2

Ca(OH)2 + CO2 → CaCO3 + H2O


Compounds




Properties


Calcium carbonate is white fluffy powder and is almost insoluble in water.

It reacts with strong acids, releasing carbon dioxide.

CaCO3(s) + 2 HCl(aq) → CaCl2(aq) + CO2(g) + H2O(l)

CaCO3(s) → CaO(s) + CO2(g)

It releases carbon dioxide on heating to form calcium oxide.

Calcium carbonate reacts with water that is saturated with carbon dioxide to form the soluble calcium bicarbonate.

CaCO3 + CO2 + H2O → Ca(HCO3)2


Compounds




Uses


In the form of marble as construction material.

It is used in production of quick lime.

The mixture of calcium carbonate and magnesium carbonate is used as flux in the extraction of metal like iron.

It is used as antacid in medicines, as abrasive in tooth paste and as filler in cosmetic materials.


Compounds




Plaster of Paris (2CaSO4.H2O)


Plaster of Paris is prepared by heating gypsum at 120°C in rotary kilns, where it gets partially dehydrated.

The temperature should be kept below 140°C otherwise further dehydration will take place and the setting property of the plaster will be partially reduced.

Plaster of Paris is a building material used for coating walls and ceilings.


Compounds




Properties


It is a white powder.

When mixed with water (1/3 of its mass), it evolves heat and quickly sets to a hard porous mass within 5 to 15 minutes. During setting, a slight expansion (about 1%) in volume occurs so that it fills the mould completely and takes a sharp impression. The process of setting occurs as follows:

The first step is called the setting stage, and the second, the hardening stage. The setting of plaster of Paris is catalyzed by sodium chloride, while it is reduced by borax, or alum.


Compounds




Uses


In surgery for setting broken or fractured bones.

For making casts for statues, in dentistry, for surgical instruments, and toys etc.

In making black board chalks, and statues.

In construction industry.


Compounds




Cement


It was first introduced by Joseph Aspidin in England in 1824. It is also called Portland because it is similar to natural lime stone available in the mines of stone in the ‘isle of Portland’.

A cement is a binder, a substance that sets and hardens independently, and can bind other materials together.


Compounds



Mineral Coal and Mineral Oil PetroleumStructure of AtomThe s-Block Elements Lithium and SodiumCompounds of Calcium

Cement is made by heating calcium carbonate with small quantities of clay to 1450 °C in a kiln, in a process known as calcination, whereby a molecule of carbon dioxide is liberated from the calcium carbonate to form calcium oxide which is then blended with the other materials that have been included in the mix. The resulting hard substance, called 'clinker', is then ground with a small amount of gypsum into a powder to make ‘Ordinary Portland Cement’.

Cement


Compounds




Properties


Due to presence of iron, it appears like ash colour.

Cement if brought in contact with water, start gaining strength and becomes hard.

The quality of portland cement is known by silica module and alumina module.


Compounds




Setting of Cement


When cement is mixed with water, it sets down and a hard substance is formed. This is called setting of cement.

The reason for addition of gypsum is to slow down the time of setting of cement so that it can become sufficiently hard. Its primary strength is seven days.


Compounds




Uses


Cement concrete is used for the construction of various structures like buildings, bridges. water tanks, tunnels, docks, harbors etc. Cement is used to manufacture lamp posts, telephone posts, railway sleepers, piles etc. For manufacturing cement pipes, garden seats, dust bins, flower pots etc., cement is commonly used.

Cement is used widely for the construction of various structures. Some of them are listed below: Cement slurry is used for filling cracks in concrete structures.

Element Elements and Compounds Compounds of Calcium Structure of Atom Compounds A compound is a...

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