Plaster of Paris

Q.

Write an equation to show the reaction between Plaster Of Paris and water

Q.

What is obtained when gypsum is heated at $373\mathrm{K}$?

Q.

What is dead burnt plaster?

Q.

Why is Plaster of Paris written as $\left({\mathrm{CaSO}}_4.\frac{1}{2}{\mathrm{H}}_2\mathrm{O}\right)$? How is it possible to have half a water molecule attached to CaSO₄?

Q. Question 13
Plaster of Paris should be stored in a moisture-proof container. Explain why.

Q.

What are the properties of plaster of paris?

Q. Plaster of Paris is obtained by:

1. adding sulphuric acid to calcium hydroxide.
2. heating gypsum to ${120}^{\circ }C$.
3. heating gypsum to a very low temperature.
4. adding water to calcium sulphate.

Q.

What happens when gypsum heated with $373\mathrm{K}$?

Q.

What are the different types of plaster of paris?

Q.

Write a balanced chemical reaction involved in heating Gypsum at 100^oC.

Q.

What is water of crystallization? Give the name and formulae of any five salts that have water of crystallization.

Q.

What happens when plaster of paris is heated ?

Q.

Plaster of Paris is prepared by heating one of the following to a temperature of ${100}^{o}C$. This is :

(a) $CaS{O}_{3}2H_{2}O$

(b) $CaC{l}_{2}2H_{2}O$

(c) $CaC{O}_3.2H_{2}O$

(d) $CaS{O}_4.2H_{2}O$

Q.

Write the formula for the water of crystallisation for hydrated copper sulphate.

Q.

Plaster of Paris is a _______ hydrate of calcium sulphate.

Q.

Assertion: Plaster of paris is stored in a moisture proof container.

Reason: Plaster of paris set into a hard mass on wetting with water to form anhydrous Calcium sulphate.

1. Both A and R are true and R is the correct explanation of A.

2. Both A and R are true and R is not the correct explanation of A.

3. A is true but R is false.

4. A is false but R is true.​

Q.

What happens when plaster of paris is mixed with water ?

Q.

(a) What is plaster of Paris? Write the chemical formula of plaster of Paris.

(b) How is plaster of Paris prepared? Write the chemical equation of the reaction involved.

(c) Explain why plaster of Paris should be stored in a moisture-proof container.

(d) State two important uses of plaster of Paris.

Q.

Write the chemical reaction for the change of Gypsum into Plaster of Paris.

Q. Plaster of Paris is obtained by:

1. adding water to calcium sulphate.
2. adding sulphuric acid to calcium hydroxide.
3. heating gypsum to a very low temperature.
4. heating gypsum to ${120}^{\circ }C$.

Q.

On heating, blue copper sulfate crystals become white.

Q. What is the chemical formula of gypsum?

1. ${\text{CaSO}}_4.2{\text{H}}_2\text{O}$
2. ${\text{CuSO}}_4.5{\text{H}}_2\text{O}$
3. ${\text{Na}}_2{\text{CO}}_3.10{\text{H}}_2\text{O}$
4. ${\text{CaOCl}}_2$

Q.

Identify the compound of calcium that is used for plastering fractured bones. With the help of a chemical equation show, how is it prepared, and whether special precautions should be taken during the preparation of this compound?

Q. Chemically, Plaster of Paris is calcium sulphate hemihydrate, i.e. containing half molecule of water of crystallisation. It is represented by the formula, ${\text{CaSO}}_4.\frac{1}{2}{\text{H}}_2\text{O}$. Half molecule of water of crystallisation means that one water molecule is shared by two formula units of $CaS{O}_4$. Hence we also represent its formula as $(CaS{O}_4{)}_2.H_{2}O$. The name, Plaster of Paris, was given to this compound because for the first time, it was made from gypsum which was mainly found in Paris. Gypsum has the chemical formula, $CaS{O}_4.2H_{2}O$. When plaster of Paris is mixed with water it sets into a hard mass.

(a) The difference in number of water molecules present as water of crystallisation in gypsum and Plaster of paris is
(i) 5/2 (ii) 2 (iii)1/2 (iv) 3/2

(b) Plaster of Paris hardens by
(i) giving off $C{O}_2$ (ii) changing into $CaC{O}_3$
(iii) combining with water (iv) giving out water

(c) Plaster of Paris is obtained by
(i) adding water to calcium sulphate
(ii) adding sulphuric acid to calcium hydroxide
(iii) heating gypsum to a very high temperature
(iv) heating gypsum to 373 K.
[3 Marks]

Q. Question 47.
A sulphate salt of group 2 element of the periodic table is a white, soft substance, which can be moulded into different shapes by making its dough. When this compound is left in the open for some time, it becomes a solid mass and cannot be used for moulding purposes.
Identify the sulphate salt and why does it show such a behaviour ?
Write down the reaction involved.

Q.

When Gypsum is heated to 393K, it forms:

1. ${\mathrm{CaSO}}_4.1/2{\mathrm{H}}_2\mathrm{O}$

2. Dead burnt plaster

3. ${\mathrm{CaSO}}_4.5{\mathrm{H}}_2\mathrm{O}$

4. Anhydrous ${\mathrm{CaSO}}_4$

Q.

A white chemical compound becomes hard on mixing with proper quantity of water. It is also used in surgery to maintain joints in a fixed position. Name the chemical compound.

Q.

What is dead plaster or burnt plaster and how it is made?

Q.

One molecule of hydrated ${\mathrm{CuSO}}_4$ contains how many molecules of water of crystallization?

Q.

The reddish-brown fume coming out when lead nitrate is heated is known as

1. Nitrogen trioxide

2. Nitrogen monoxide

3. Nitrogen

4. Nitrogen dioxide