Calcium Carbonate and Calcium Sulphate(Plaster of Paris) MCQ

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Calcium Carbonate - CaCO3 and Calcium Sulphate(Plaster of Paris) - CaSO4·1⁄2H2O is considered one of the most asked concept.
42 Questions around this concept.

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What is the role of gypsum, $\mathrm{CaSO}_4 \cdot 2 \mathrm{H}_2 \mathrm{O}$ in setting of cement ? Identify the correct option from the following :

to provide water molecules for hydration process

to help to remove water molecules

to slow down the setting process

to fasten the settings process

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Match list-I with List-II for the composition of substances and select the correct answer using the code given below the lists

	List - I Substances		List - II Composition
(A)	Plaster of Paris	(i)	CaSO₄.2H₂O
(B)	Epsomite	(ii)	$\mathrm{CaSO}_4 \frac{1}{2} \mathrm{H}_2 \mathrm{O}$
(C)	Kieserite	(iii)	MgSO₄.7H₂O
(D)	Gypsum	(iv)	MgSO₄.H₂O
		(v)	CaSO₄

Code:

(A) (B) (C) (D)

(i) (ii) (iii) (v)

(iv) (iii) (ii) (i)

(iii) (iv) (i) (ii)

(ii) (iii) (iv) (i)

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In curing cement plasters water is sprinkled from time to time. This helps in:

keeping it cool

developing interlocking needle-like crystals of hydrated silicates

hydrating sand and gravel mixed with cement

converting sand into silicic acid.

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Which one of the following alkaline earth metal sulfates has its hydration enthalpy greater than its lattice enthalpy?

CaSO₄

BeSO₄

BaSO₄

SrSO₄

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The substance not likely to contain $CaCO_3$ is

a marble statue

calcined gypsum

sea shells

dolomite.

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Solubility of the alkaline earth's metal sulphates in water decreases in the sequence:

Sr > Ca > Mg > Ba

Ba > Mg > Sr > Ca

Mg > Ca > Sr > Ba

Ca > Sr > Ba > Mg

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Plaster of paris is prepared on heating -

Quick lime

Slaked lime

Lime stone

Gypsum

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What is reason of temporary hardness of water?

$\mathrm{Na}_2 \mathrm{SO}_4$

$\mathrm{CaCl}_2$

NaCl

$\mathrm{Ca}\left(\mathrm{HCO}_3\right)_2$

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Calcium Carbonate - CaCO3 and Calcium Sulphate(Plaster of Paris) - CaSO4·1⁄2H2O

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:

$\mathrm{Ca}(\mathrm{O}\mathrm{H})_{2}+\mathrm{CO}_{2} \rightarrow \mathrm{CaCO}_{3}+\mathrm{H_{2}} \mathrm{O}$

$\mathrm{CaCl}_{2}+\mathrm{Na}_{2} \mathrm{CO}_{3} \longrightarrow \mathrm{CaCO}_{3}+2 \mathrm{NaCl}$

Uses

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

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

Preparation
It is obtained when gypsum, CaSO4·2H2O, 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 crystallisation 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 moulds for casting.