Water of crystallization

Beāte Laķe

Teacher of biology

Riga Secondary Night (Shift) School No.14

H2O crystals

In rocks water of crystallization can be found 20 times more

than in oceans and sees

Crystals that have locked up water in themselves for millions of years..

Quartz

While distributing water from crystals we can learn about the development of the Earth

Crystals of gympsum

Stalactites made by water in Slovenia

Crystalhydrates Crystal hydrate is a hard crystal matter that has chemicly joined with water -

-water of crystallization (e.g., AlCl3·6H2O, BeCl3·4H2O etc.).

While heating crystalhydrates, water of crystallization can fully or partly be

saparated.

Crystalhydtare

                              

CuSO4 · 5H2O

          

No-water substance

                              

CuSO4

+ Water of crystallization 5H2O

No-water CuSO4 when added water– heat is caused to spread–

So a chemical reaction is happening.

Different colours of crystalhydrates:

Cu(NO3)2·6H2O blue.

CoCl2 ·6H2O red

CuSO4·5H2O blue.

CuSO4·1H2O whites.

CuSO4·5H2O

[Cu(4H2O)]SO4.H2O- formula of complex combination.

Pink colour of Mn(II) crystalhydrates, e.g.,

Mn(NO3)2·6H2O and MnCl2·2H2O

MnCl2·2H2O

Mn(NO3)2·6H2O

Ni(NO3)2x6H2O.

Gympsum CaSO4·2H2O

Crystals of gypsum can reach up to 15 m

Heated CaSO4·½H2O is used in medicine, art, construction.

Exercise

• 74,25 g zinc nitrate’s crystalhydrate consists of 27,00 g of water.

Calculate the formula of the crystalhydrate!

Cluea) A formula of the unknown crystalhydrate is

written as Zn(NO3)2·xH2O, where x shows, how many moles of water contains the particular crystalhydrate to each mole of no-water salt.

• b) Calculate the no-water salt’s mass in the

crystalhydrate.• m(Zn(NO3)2) = m(Zn(NO3)2·nH2O) – m(H2O) =

74,25 – 27,00 = 47,25 g

Further…c) Calculate the no-water salt’s and water’s

amount in the crystalhydrate.

Further..• d) To form the formula the crystalhydrate,

calculate how many moles of water are joined with one mole of no-water salt.

• With 0,25 moles Zn(NO3)2 are joined 1,5 moles of water.

With 1 mole Zn(NO3)2 are joined x moles of water

• e) Calculate x.

Answer.

• f) Write the formula of the crystalhydrate. Zn(NO3)2·6H2O

Bibliography• Ahmetovs N., “Neorganiskā ķīmija” – R: Zvaigzne, 1978.

• Feldmanis F., Rudzītis G.,“Neorganiskā ķīmija” – R: Zvaigzne, 1981.

• Valdis Segliņš Minerāli un ieži.-RaKa, 2007.g.

• www.google.com

• www.webelements.com

• www.webminerals.com