Question

how many water molecules does hydrated calcium sulphate contains (a) 5 (b) 10 (c) 7 (d) 2​

Answer 1

Answer:

caso4 .1/2 h2o is plaster of paris

on adding water we get

caso4.2h20 (gypsum)

the answere is 2

Answer 2

Answer:

The correct answer is Option D : $2$

Explanation:

Hydrated calcium sulphate can be represented as : $[CaSO_4.xH_2O]$

Molar mass of the hydrated compounds is the sum of molar masses of $CaSO_4$ and $x$ times $H_2O$.

Molar mass $=136+18x$

The percentage of water in this hydrated compound is :

$18x*\frac{100}{136+18x}$

$=21$

Solving for $x$,

We get $x=2$

The hydrated compound is : $[CaSO_4.2H_2O]$

Hence, the number of water molecules is $2$.