Question

Why is the temperature maintained around 393k during preparation of plaster of paris

Answer 1

As plaster of Paris prepared from Gypsum which contains water,in order to remove that water the BP is maintained.
Here if do not maintain 393K ,it set as hard mass..

Answer 2

For the preparation of plaster of paris, the temperature must be maintained at around 393K.

We are required to find the reason for the temperature maintenance of around 393K during the preparation of the plaster of paris.

The chemical formula of the plaster of Paris is 2CaSO₄.1/2H₂O while for gypsum is 2CaSO₄.2H₂O and for dead burnt

When the gypsum (2CaSO₄.2H₂O) is heated at 393K, it results in the formation plaster of paris 2CaSO₄.1/2H₂O and 3 molecules of water.

2CaSO₄.2H₂O -----> 2CaSO₄.1/2H₂O+3HO      (At 393K)

   (Gypsum)            (Plaster of paris)      (water)

When the temperature is above 393 K, The plaster of paris is further dehydrated to form anhydrous calcium sulfate known as dead burnt plaster.

2CaSO₄.1/2H₂O−→−−>2CaSO₄+H2O   (above 393K)

                              (Dead burnt plaster)

Therefore, For the preparation of plaster of paris the temperature must be maintained at around 393K.

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