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NEET levelSingle correct optionDifficulty 1 of 3sb167

Gypsum, $CaSO X_{4} \cdot 2 H X_{2} O$ , when heated to about 393 K, gives

A $CaS$
B $CaSO X_{4}$
C $CaO$
D $CaSO X_{4} \cdot \frac{1}{2} H X_{2} O$

Answer: D

At about 393 K gypsum loses three-halves of a water molecule per formula unit and becomes plaster of Paris,

(CaSO X_{4}) X_{2} \cdot H X_{2} O

. Complete dehydration to

CaSO X_{4}

needs higher temperature.

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