Question

When one mole of gypsum is heated to 393 k temperature, what is the loss in mass?

Answer 1

When one mole of gypsum is heated to 393 K, the loss in mass of gypsum is 136 g.

 1) The molecular formula of gypsum is CaSO4.2H2O.  

2) Therefore, the molecular mass of gypsum is 40 g + 32 g + 64 g + 2 ( 2 g + 16 g) = 172 g.  

3) On heating gypsum to 393 K, it completely loses its water of crystallisation, due to which there is a loss in mass.  

4) The mass of water molecule in gypsum is 36 g (2H2O). Therefore, the loss in mass of gypsum on heating it to 393 K is 172 g - 36 g = 136 g.