Q7 / 160 · AP EAMCET 2004 · Chemistry
In the hardening stage of plaster of paris, the compound formed is
- A$\mathrm{CaSO}_4$
- B$Orthorhombic$ $\mathrm{CaSO}_4 \cdot 2 \mathrm{H}_2 \mathrm{O}$
- C$\mathrm{CaSO}_4 \cdot \mathrm{H}_2 \mathrm{O}$
- Correct answerD$Monoclinic$ $\mathrm{CaSO}_4 \cdot 2 \mathrm{H}_2 \mathrm{O}$
Solution
Plaster of paris absorb water to form monoclinic gypsum which is a hard substance.
$$
\mathrm{CaSO}_4 \cdot \frac{1}{2} \mathrm{H}_2 \mathrm{O} \stackrel{3 / 2 \mathrm{H}_2 \mathrm{O}}{\longrightarrow} \mathrm{CaSO}_4 \cdot 2 \mathrm{H}_2 \mathrm{O}
$$
(monoclinic gypsum)
Hence, the correct answer is option: 'D'.