Question

Which of the following is known as dead burnt?
A. Gypsum
B. Plaster of Paris
C. Anhydrite
D. None of these

Answer 1

Hint: Plaster is generally made up of calcium sulphate which is basically used to make pots, chalks, and other decorative items rather than this the main basic use of plaster is in medical use i.e. to fix fractured bones.

Complete step by step answer:
Dead burnt plaster is anhydrous calcium sulphate represented by the chemical formula$CaS{{O}_{4}}$. There is an interesting logic why it is named as dead burnt plastic as we all know that plaster of Paris is set when it is moistened with water but anhydrous calcium sulphate is fail to set up when it is moistened with so as a result it is known by the name dead burnt.
Dead burnt plaster is produced which is known as anhydrite or anhydrous calcium sulphate is generally have to start product gypsum which is represented by the chemical formula $CaS{{O}_{4}}.2{{H}_{2}}O$ when it is further heated at the temperature of $120{}^\circ $C then it gets turned into plaster of Paris having the chemical formula $CaS{{O}_{4}}.1/2{{H}_{2}}O$ and, when plaster of Paris heated above 393K its water of crystallization, is completely lost and we are left with anhydrous calcium sulphate having the chemical formula $CaS{{O}_{4}}$ known by the name anhydrite.
So, the correct answer is “Option C”.

Note: Calcium sulphate is an inorganic compound. It has many applications in various industries. All forms of calcium sulphate are white in color, solid in state, and generally are insoluble in water. It causes permanent hardness in water.