There were times long ago, when everything was simpler. In middle school (formerly the primary school) and taught at the high school construction chemicals in a very simplified way to explain the basic rights-friendly chemistry. In college course material is greatly expanded, but even then he discovers the students all the really great mysteries ...
secrets will be uncovered today seemingly trivial and obvious associations which are salts. Sole or middle school students and high school nightmare: DW during those less than six years, during which I give private lessons, have not met with more prohibitive for young people theme: P Today, however, will not virtually nothing about the methods of obtaining salt, today I will tell about what salts are in fact ... both in the solid state and in aqueous solutions.
Take a simple example at the beginning - FeCl 3 , or ferric chloride (III). Anhydrous salt solid-state structure of the iodide of bismuth (III) BII 3 and forms hygroscopic crystals, dark green or black. This salt dissolved in water gives a strongly acidic solutions. So let's look into this solution. As you know, the metal ions in water are not simple cations, but the so-called. akwajonami. In the case of iron (III) that is akwajonem heksaakważelaza cation (III) [Fe (H 2 O) 6 ] 3 + . In aqueous solutions, such akwajony may behave as Bronsted acids by placing a proton H + . This is also true in the case [Fe (H 2 O) 6 ] 3 + , as illustrated following equations:
[Fe (H 2 O) 6 ] 3 + + H 2 O -> [Fe (H 2 O) 5 (OH)] 2 + + [H 3 O] +
[Fe(H 2 O) 5 (OH)] 2+ + H 2 O -> [Fe (H 2 O) 4 (OH) 2 ] + [ H 3 O] +
This process also affects the color of the solution. [Fe (H 2 O) 6 ] 3 + color is purple, but anyone who has seen salt solutions of iron (III) know that they are color brązowożółtej. For this situation arising due to hydrolysis correspond hydrokso complexes of iron (III). Now, back to the ferric chloride (III). The solution Water can be crystallized hydrate FeCl 3 × 6H 2 About , orange-brown color. Properly stored, however, the model of the hydrate is trans - [FeCl 2 (H 2 O) 4 ] Cl × 2H 2 O which contains The structure of ion on the construction depicted in the figure below:
But, but ... It's not all!;) The effect of hydrolysis [Fe (H 2 O) 6 ] 3 + can also create a bridge structure, including [(H 2 O) 5 feof (H 2 O) 5 ] 4 + :
this cation is already quite an uncle;) bridge Fe-O-Fe is linear, as seen above, which indicates the presence of binding (dp) π formed by the overlap of d orbitals of iron and p orbitals of oxygen. The structure of the cation determined by X-ray structural salt crystallized [(H 2 O) 5 Fe (μ-O) (H 2 O) 5 ] [ClO 4 ] 4 × (18-crown-6) 2 × 2H 2 About . In this system, crown ether is linked by hydrogen bonds and coordinated with the iron atoms of water molecules: 
Crown ether 18-crown-6 has the following structure: 
interesting case is Fei 3 . This salt decomposes very easily:
2 Fei 3 -> 2 Fei 2 + I 2
this compound can not be obtained by reaction of Fe 3 + of iodides, iron (III) is reduced to Fe 2 + and releases the free iodine. However, you can address the problem and isolate Fei 3 under neutral conditions (eg, argon) in the following reaction:
2 Fe (CO) 4 I 2 + I 2 -> 2 Fei 3 + 8 CO
No! As it can not, as you can?;) Let's look at yet another Solom iron (III))
Anhydrous Fe (ClO 4 ) 3 is solid yellow. Commercially available in hydrate form of a rather different water content, and it is in response Fe 2 About 3 × H 2 About with aqueous HClO 4 . Depending on the degree of contamination by chlorides may be pale mauve (less than 0.005% of chloride content), or yellow.
sulphate (VI) iron (III) Fe 2 (SO 4 ) 3 create white or beige crystals, is available as a hydrate Fe 2 (SO 4 ) 3 × 5H2O . Nitrate (V), iron (III), in turn, creates a colorless or pale violet crystals of hydrate of formula Fe (NO 3 ) 3 × 9H 2 About , whose record looks correct, however, follows: [Fe (H 2 O) 6 ] [NO 3 ] 3 × 3H 2 About . Is obtained by the reaction of iron oxides with concentrated HNO 3 . However, purple hexahydrate Fe (NO 3 ) 3 × 6H 2 About (and correctly: [Fe (H 2 O) 6 ] [NO 3 ] 3 ) is obtained by reacting Fe 2 About 3 × H 2 About of HNO 3 .
enough for today! Coming soon will be a continuation of the story of salt;)
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