Question

Dead burnt plaster is

• A. $CaS{O}_4$
  
  
• B. $CaS{O}_{4.}\frac{1}{2}{H}_{2}O$
  
  
  
• C. $CaS{O}_{4.}2H_{2}O$
  
• D. $CaS{O}_{4.}{H}_{2}O$
  

Answer 1

The correct option is D $CaS{O}_{4.}{H}_{2}O$


Dead burnt plaster is anhydrous calcium sulphate i.e., $CaS{O}_4$

Dead burnt plaster is formed when gypsum $\left(CaS{O}_4.2H_{2}O\right)$ is heated to $393K$. This causes loss of water of crystallisation and forms anhydrous calcium sulphate.

Hence, option (A) is correct