Crystalhydrates Crystal hydrate is a hard crystal matter that has chemicly joined with water - -water of crystallization -water of crystallization (e.g., AlCl 3 ·6H 2 O, BeCl 3 ·4H 2 O etc.). While heating crystalhydrates, water of crystallization can fully or partly be saparated. CuSO 4 · 5H 2 O Crystalhydtare CuSO 4 · 5H 2 O No-water substance CuSO 4 + 5H 2 O Water of crystallization 5H 2 O
No-water CuSO 4 when added water– heat is caused to spread– So a chemical reaction is happening.
Different colours of crystalhydrates: Cu(NO 3 ) 2 ·6H 2 O blue. CoCl 2 ·6H 2 O red CuSO 4 ·5H 2 O blue. CuSO 4 ·1H 2 O whites. CuSO 4 ·5H2O
[Cu(4H 2 O)]SO 4. H 2 O- formula of complex combination.
Pink colour of Mn(II) crystalhydrates, e.g., Mn(NO 3 ) 2 ·6H 2 O and MnCl 2 ·2H 2 O MnCl 2 ·2H 2 O Mn(NO 3 ) 2 ·6H 2 O
Heated CaSO 4 ·½H 2 O 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!
Clue a) A formula of the unknown crystalhydrate is written as Zn(NO 3 ) 2 ·xH 2 O, 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(NO 3 ) 2 ) = m(Zn(NO 3 ) 2 ·nH 2 O) – m(H 2 O) = 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(NO 3 ) 2 are joined 1,5 moles of water. With 1 mole Zn(NO 3 ) 2 are joined x moles of water e) Calculate x.
Answer. f) Write the formula of the crystalhydrate. Zn(NO 3 ) 2 ·6H 2 O
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