The formula of gypsum and that of plaster of parls are CaSO4.xH2O and CaSO4.yH2O respectively. The difference x-y equals to;

1) 1
2) 3/2
3) 5/2
4) 1/2

Help me

Explanation:

Given formula of Gypsum:

               CaSO₄. xH₂O,

       True formula:

              CaSO₄. 2H₂O,  x  = 2

Formula of plaster of paris  = CaSO₄. H₂O,

               y  =  

The difference between x and y; x - y:

               x  - y = 2 -    =  

so here we go

atomic mass

239 + 1 = y + 134 + 3 combine like terms

240 = y + 137             subtract 137 from both terms

240 - 137 = y

103 = y

atomic number

94 = z +54 + 0

94 = z + 54               subtract 54 from both sides.

40 = z

answer

the answer is d. 74.02