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Adobe Scan 17 Oct 2020

Many salts contain water molecules bonded to their crystalline structure. This water is called water of crystallization. Heating hydrated salts, which contain water of crystallization, causes the water molecules to break free from the crystalline structure. The water is removed, leaving behind an anhydrous salt without water of crystallization.

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45 views2 pages

Adobe Scan 17 Oct 2020

Many salts contain water molecules bonded to their crystalline structure. This water is called water of crystallization. Heating hydrated salts, which contain water of crystallization, causes the water molecules to break free from the crystalline structure. The water is removed, leaving behind an anhydrous salt without water of crystallization.

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Many salts combine with water molecules to form

crystals. These water


molecules are known as water of
crystallisation. The water of crystallisation
can be removed by heating hydrated salts (Figure
12.1).

When hydrated salts


Salts that contain water are heated, the water of Salts that do not
of crystallisation are crystallisation is given out contain water of
called hydrated salts. crystallisation are
The amount of called anhydrous salts
heating
water crystallised Anhydrous salts are
- 5H,0
in a hydrated salt is often powders.
indicated after the
dot'.' in its chemical
formula.

blue crystals: white powder


hydrated copper(0) +5H,0 anhydrous copper(ll)
suifate (CuSO, .5H,O) hydration sulfate (CusO,)

The hydrated salt can be


obtained from the anhydrous
salt by adding water.
insoluble salts: invoives
Preparation of soluble salts: Preparation of
a solutionthat contains its positive
metal+ acid salt+ hydrogen mixing
contains its
oxide acid s a l t + water ion with another solution which
metal +

ion. This results in the precipitation


salt +water negative
metal hydroxide +acid water+ carbon dioxide of the insoluble salt.
metal carbonate + acid salt+

Solubility of salts: all nitrates are soluble and


most chlorides (except AgCl PbCI) and most
are soluble.
sulphates (except BaSo, PbSO)
However most carbonates are insoluble
[except Na,CO, K,CO, (NH),COJ.

Salts: substances formed when the hydrogen


of an acid is replaced (partialy or wholly) by a
metal, e.g. sulphate salts from sulphuric acid,
such as MgSO, magnesium sulphate, CuSO
copper(l1) sulphate, etc
Testing for cations: cations
Testing for anions: tests to
can be identified by their
identify the following anions
reaction with aqueous sodium Identification of gases:
hydroxide or aqueous CO C,I,NO and SO.
describe tests to identify the
ammonia, e.g A/, OCa, Cu following gases: ammonia,
Fe Fe Pb Zn NH, carbon dioxide, chlorine,
hydrogen, oxygen and

sulphur dioxide

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