Waters of Crystallisation

Question 1

Define hydrates

Answer 1

Compounds that contain water in the form of H2O

Question 2

Define hydrous

Answer 2

With water

Question 3

Define anhydrous

Answer 3

Without water

Question 4

What is the method for determining how many moles of water are in a hydrous molecule?

Answer 4

Mass of crucible (g) A
Mass of hydrous molecule and crucible (g) B
Mass of hydrous molecule (g) C=B-A
Mass after heating (g)
Mass after reheating (g) D
Mass of anhydrous molecule (g) E = D-A
Mass of H2O evolved (g) F = C-E

Moles H2O = mass of water evolved / molecular mass of water
Moles of anhydrous molecule = mass of anhydrous molecule / molecular mass of anhydrous molecule

Number of moles of water in hydrous molecule = moles of water / moles of anhydrous molecule