i) On adding dilute HCl to copper oxide powder, the solution formed is blue green. a) Identify the compound formed which gives blue-green colour to the solution. b) Write balanced chemical equation to the above reaction. c) On the basis of the above reaction, what should be the nature of copper oxide? ii) Write the chemical equation involved in the preparation of plaster of Paris. Write any two uses of plaster of Paris.

Dear student,

Please find below the solution for your 2nd question-

(ii) Preparation of Plaster of paris-

Limestone is also called calcium carbonate. It occurs in the nature as chalk, marble etc.It is a white solid which is insoluble in water. It reacts with dilute sulphuric acid and form calcium sulphate as 

$CaC{O}_3 + H_{2}S{O}_4 \to CaS{O}_4 + C{O}_2 + H_{2}0$

The hydrated form of calcium sulphate is called gypsum $CaS{O}_4.2H_{2}O$

Plaster of paris is prepared heating gypsum at 393K as 

$2CaS{O}_4 . 2H_{2}O \stackrel{393 K }{\to } 2CaS{O}_4 . \frac{1}{2}{H}_{2}O + 3H_{2}O$

Plaster of paris is also called as calcium sulphate hemihydrate.

Uses of Plaster of paris-

• It is used in making toys, materials for decoration and for making smooth surfaces.
• It is used in surgical bandages by doctors for supporting fractured bones in the right position.
• It is used in making casts of statues, moulds for pottery and ceramics. It is also used in building material.
• It is used in dentistry.

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