Water of crystallisation

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  • Created by: racheon
  • Created on: 03-03-14 11:41
Define hydrated.
A crystalline compound containing water molecules.
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Define anhydrous.
A substance that contains no water molecules.
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Define water of crystallisation.
Water molecules that form an essential part of the crystalline structure of a compound.
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How is the empirical formula of the compound separated from the water of crystallisation?
By a dot.
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Hydrated copper sulfate has 5 H2O molecules for each unit of CuSO4. What is it's empirical formula?
CuSO4.5H2O.
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What is the empirical formula of colbat chloride hexahydrate?
CoCl2.6H2O.
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What is the empirical forumla of sodium sulfate decahydrate?
Na2SO4.10H2O.
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What do you use to work out the formula of a hydrate salt?
Percentage or mass compositions.
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What method do you use to work out the formula of a hydrate salt?
The same method you would use for empirical formula, but adding an extra step for the dot formula.
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What element do you use to work out how many water molecules you have?
Hydrogen.
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If you have any extra oxygen atoms after working out the dot formula, what do they belong to?
The substance.
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The empirical formula of hydrated magnesium chloride is MgCl2H10O5. What is it's dot formula?
MgCl2.5H2O.
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The empirical formula of hydrated sodium carbonate is Na2CH20O13. What is it's dot formula?
NaCO3.10H2O.
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The empirical formula of hydrated calcium nitrate is CaN2H8O10. What is it's dot formula?
Ca(NO3)2.4H2O.
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How do you determine the formula of a hyrdrated salt?
1. Heat it so the water evaporates. 2. You need the mass of the hydrated salt, the anhydrous salt and the water lost.
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The mass of MgSO4.xH2O is 4.312g. The mass of MgSO4 is 2.107g. The mass of H2O is 2.205g. What is x?
1. Calculate the amount, in mol, of MgSO4: M(MgSO2)=24.3+32.1+(16x4)=120.4g mol^-1. n(MgSO4)=2.107/120.4=0.0175mol. 2. Calculate the amount, in mol, of water: 2.205/18=0.1225. 3. Determine the formula of the hydrated salt: 0.0175:0.01225=1:7. x=7.
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How do you work out the amount, in moles, when talking about mass?
n=m/M.
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Other cards in this set

Card 2

Front

Define anhydrous.

Back

A substance that contains no water molecules.

Card 3

Front

Define water of crystallisation.

Back

Preview of the front of card 3

Card 4

Front

How is the empirical formula of the compound separated from the water of crystallisation?

Back

Preview of the front of card 4

Card 5

Front

Hydrated copper sulfate has 5 H2O molecules for each unit of CuSO4. What is it's empirical formula?

Back

Preview of the front of card 5
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