Plaster of Paris, $(CaSO X_{4}) X_{2} \cdot H X_{2} O$ (Ca 40, S 32, O 16, H 1), sets to a hard mass of gypsum on mixing with water. The mass of water chemically taken up when 5.80 g of plaster of Paris sets completely is

Answer: C

Setting follows

(CaSO X_{4}) X_{2} \cdot H X_{2} O + 3 H X_{2} O 2 CaSO X_{4} \cdot 2 H X_{2} O

. Molar mass of plaster of Paris is

2 (136) + 18 = 290

, so 5.80 g is 0.0200 mol and it absorbs

3 \times 0.0200 = 0.0600

mol water, which is

0.0600 \times 18 = 1.08