Water of crystallization (WC) is the number of molecules of water present in one mole of a hydrated salt. Example, in iron (II) tetraoxosulphate (VI)-heptahydrate [FeSO4.7H2O], there are seven molecules of water attached to a molecule of FeSO4, that is its water of crystallization. Some other examples of salts with water of crystallization include: MgSO4.7H2O - Magnesium tetraoxosulphate(VI)-heptahydrate, (Epsom Salt) CaSO4.2H2O - Calcium tetraoxosulphate(VI)-dihydrate (Gypsum) Na2CO3.10H2O - Sodium trioxocarbonate(IV)-decahydrate (Washing Soda) CuSO4.5H2O - Copper (II) tetraoxosulphate(VI)-pentahydrate (Blue Vitriol) ZnSO4.7H2O - Zinc tetraoxosulphate(VI)-heptahydrate (White Vitriol) Cu(NO3)2.3H2O - Copper (II) trioxonitrate(V)-trihydrate From the above examples, it can be observed that each salt has a definite number of molecules of water of crystallization attached to it. Therefore, it can also be defined as the definite amount of water some substances chemically combine wi
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