S Block Elements Question 139
Question: Setting of plaster of paris is
[MP PMT 1985; CPMT 1989]
Options:
A) Oxidation with atmospheric oxygen
B) Combination with atmospheric $ CO_2 $
C) Dehydration
D) Hydration to yield another hydrate
Show Answer
Answer:
Correct Answer: D
Solution:
Setting of plaster of paris is exothermic process $ CaSO_4.\frac{1}{2}H_2O\xrightarrow{H_2O}\underset{\text{Orthorhombic }}{\mathop{CaSO_4.2H_2O}} $
$ \xrightarrow{Hardening}\underset{\begin{smallmatrix} \text{Mono orthorhombic } \\ Gypsum \end{smallmatrix}}{\mathop{CaSO_4.2H_2O}} $ The setting is due to formation of another hydrate
BETA
