A suphlate slat of goup 2 elemne t of the periodic tables is a swhite soft substance which can be moluded in to different shapes by making its dough. When this compound is left in open for some time, it becomes a solid masss and cannot be used for moudling purposes . Identify the suphates salt and why does it show such a behavuiour ? Gove the reaction involved .

A suphlate slat of goup 2 elemne t of the periodic tables is a swhite

1.	A suphlate slat of goup 2 elemne t of the periodic tables is a swhite soft substance which can be moluded in to different shapes by making its dough. When this compound is left in open for some time, it becomes a solid masss and cannot be used for moudling purposes . Identify the suphates salt and why does it show such a behavuiour ? Gove the reaction involved .
Answer» The suphate salt which is used for making different shapes is plaster of paris. Its chemical name is calcium suplhate hemihyderte`(CaSO_(4)(1)/(2)H_(2)O)`. The two formula units of `CaSO_(4)` share one molecule of water . As a result , it is soft. When it is left open for some time, it absorb moistue from the atmosphere and forms gypsum which is a hard solid mass So gypsum sets as a hard solid mass and cannot be used for mouding purposes. `CaSO_(4).(1)/(2)G_(2)O+1(1)/(2)H_(2)OrarrCaSO_(4).2H_(2)O`