Some Important compounds of Calcium

Some Important compounds of Calcium

Let's know about some important compounds of Calcium!

Calcium carbonate (CaCO₃) : Physical Properties

Calcium carbonate is also called lime. It is a white fluffy powder that is insoluble in water. It occurs in nature in several forms like limestone, chalk, marble etc.

Calcium Carbonate (CaCO₃ ) : Reaction

It gets decomposed followed by the release of carbon-dioxide on heating to 1200 K. Excess

CO₂ should be avoided since it leads to the formation of water soluble Calcium hydrogen carbonate.

CaCO₃ + 1200 K --> CaO + CO₂

CaCO₃ + 2HCl --> CaCl₂ + H₂O + CO₂

CaCO₃ + H₂SO₄ --> CaSO₄ + H₂O + CO₂

Calcium carbonate (CaCO₃)

It is prepared by passing carbon dioxide through slaked lime.

Ca(OH)₂ + CO₂ --> CaCO₃ + H₂O

(Calcium Hydroxide)

Calcium Carbonate (CaCO₃)

It can also be prepared by the addition of sodium carbonate to calcium chloride.

CaCl₂ + Na₂CO₃ --> CaCO₃ + NaCl

CaCO₃ <--> CaO + CO₂

Calcium Carbonate (CaCO₃) : Uses

It is sued to manufacture of quick lime.

It is used as a flux in combination with magnesium carbonate in the extraction of metals such as iron.

It is also used as antacid, mild abrasive in tooth paste and chewing gum.

Multiple Select

What are the ways in which we can obtain Calcium Carbonate ( choose all the correct options)

• It can be prepared by passing CO₂ to slaked lime

• It is prepared by adding Potassium carbonate to calcium chloride

• It can be found in material like Marble, limestone and chalk

• It is prepared by reaction of chlorine and Milk of lime

Plaster of Paris

 $CaSO_4.\ \frac{1}{2}H_2O$  

The chemical name of Plaster of Paris is Calcium Sulphate. It is obtained by heating the gypsum  $CaSO_{4\ }.\ 2H_2O$  at 393 K

Above 393K, no water of crystallisation is left and anhydrous calcium sulphate, CaSO4 is formed. This is known as ‘ Dead Burnt Plaster’.​

Plaster of Paris: Uses

It forms a plastic mass on addition of water which

further gets hardened within 5-15 minutes.

It is extensively used in manufacturing decorating

pieces, in repairing fractured bones or sprains.

Open Ended

Fun Question: Why do you think calcium sulphate hemihydrate is called " Plaster of Paris " ?

Calcium Oxide ( CaO )

The chemical name of Quick Lime is Calcium Oxide (CaO).

It is a white amorphous

The melting point of CaO is 2870 K

It absorbs moisture and carbon dioxide when exposed to

atmosphere.

Calcium Oxide : Preparation

 $CaCO_3\ \rightarrow\ CaO\ +\ CO_2$  

It is prepared by heating limestone (CaCO3) in a kiln at a
temperature of 1070-1270 K.

Calcium Oxide : Preparation

Addition of water to CaO results in slaking of lime. Slaking of Quick lime with soda results solid soda lime. CaO being a basic oxide combines with acidic oxides at high temperature.

Calcium Oxide : Uses

It is used in manufacturing

industry to manufacture cement, dye stuffs and sodium carbonate. It is also used for the

purification of sugar.

Multiple Choice

Slaking of lime with soda results in the formation of:

• Lime Soda

• Soda lime

• Calcium Oxide

• Calcium Hydroxide

Slaked Lime [Ca(OH)₂]

The chemical name of slaked lime is Calcium Hydroxide

It is a white amorphous powder sparingly soluble in water. Solution of known as lime water and a suspension of slaked lime in water is called milk of lime.

Slaked Lime [Ca(OH)₂]

Passing carbon dioxide through aqueous

solution of lime water it turns milky due
to the formation of calcium carbonate.

Slaked Lime [Ca(OH)₂]

 $CaCO_3+\ CO_2+\ H_2O\ \rightarrow\ Ca\left(HCO_3\right)_2$  Passing excess of carbon dioxide
dissolves the precipitate to form
calcium

Slaked Lime [Ca(OH)₂]

Milk of lime reacts with chlorine to form hypochlorite, a constituent of bleaching powder. ​

 

Slaked Lime [ Ca(OH)₂] : Uses

Slaked Lime is extensively used in the

preparation of mortar, for white wash, glass

making and also in tanning industry.

Multiple Choice

______ is formed in the reaction of ______ and _______ which is a constituent of Bleaching powder

• Calcium hypochlorite, milk of lime, Chlorine

• Chlorine, Calcium hypochlorite, milk of lime

• Calcium Hypochlorite, calcium hyper chlorite, chlorine

• Milk of lime, Calcium hyper chlorite, oxygen

Cement

Combination of CaO with clay containing silica, SiO₂ along with the oxides of aluminium, iron and magnesium leads to the formation of cement

 Composition of Portland Cement​

CaO = 50-60%           SiO₂ = 20-25%​

​

Al₂O₃ = 5-10%          MgO = 2-3%​

​

Fe₂O₃ = 1-2%             SO₃ = 1-2

Formation of Cement

Strong heating of clay and lime results in their fusion followed by the formation of cement clinker which is then mixed with 2-3% by weight of gypsum (CaSO₄. 2H₂O). This leads to the formation of cement.​

 Important Ingredients of Cement

Dicalcium silicate (Ca₂SiO₄) = 26%,​

Tricalcium silicate (Ca₃SiO₅) = 51%​

Tricalcium aluminate (Ca₃Al₂O₆) = 11%​

Settling of Cement​

Addition of water to cement hydrates the molecules of the constituents. Gypsum is added in order to slow down the process of setting of the cement to make it get hardened.​

​

It is used to prepare concrete in plastering and constructing bridges, dams and buildings

Multiple Choice

_______ is added in order to slow down the process of setting of the cement to make it get hardened.

• Calcium oxide

• Gypsum

• Plaster Of Paris

• Calcium Hydroxide

A seminar By Sanchana Saravanan and Kolli Harika