Describe the methods for producing aluminates, ferrites and ferrates, as well as their scope. Write the equations of the corresponding chemical reactions
Aluminates – salts of non-existent metaaluminic acid (HalO2) can be obtained as follows:
1) Alloying aluminum oxide with sodium oxide at 1200 0С:
Al2O3 + Na2O = 2NaAlO2
2) Alloying aluminum oxide with metal hydroxide at 800 0С:
Al (OH) 3 + NaOH = NaAlO2 + 2H2O.
3) Fusion of alumina with carbonate at 1000 0С:
Al2O3 + Na2CO3 = 2NaAlO2 + CO22 ↑
4) Dissolution of aluminum in molten sodium hydroxide at 400 0С:
2Al + 2NaOH + 2H2O = 2NaAlO2 + 3H2 ↑
5) Reactions of aluminum hydroxide with alkalis:
When a weak alkali solution acts on freshly precipitated aluminum hydroxide, sodium tetrahydroxoaluminate is formed:
Al (OH) 3 + NaOH = Na [Al (OH) 4] (sodium tetrahydroxoaluminate);
Under the action of excess alkali on the freshly precipitated aluminum hydroxide, sodium hexahydroxoaluminate is formed.
Al (OH) 3 + 3NaOH = Na3 [Al (OH) 6] (sodium hexahydroxoaluminate).
When heated at about 800 ° C, sodium tetrahydroxoaluminate is dehydrated:
Na [Al (OH) 4] = NaAlO2 + 2H2O
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