I am having trouble on knowing what products are formed in a chemical reaction, such as these :
i) aluminium oxide and sodium hydroxide
Al2o3 + 2NaOH + 3H2O -> NaAl(OH)4
How do we know that we have to add H2O? And how we know that the product is NaAl(OH)4 ? Why can't it be NaAlO3 ?
ii) silicon dioxide with sodium hydroxide
SiO2 + 2NaOH-> Na2SiO3 + H2O
How do we know that the salt is Na2SiO3 ? Why can't it be Na2SiO2 ? I'm really confused.. And why this reaction no need to add water?
iii) Al2Cl6 + H2O -> 2Al(OH)3 +6HCl
SiCl4 + 4H2O -> SiO2 . 2H2O + 4H2O
Why not Si(OH)4? And why not Al2O3. H2O?
Are there any formula for these? Or they just happen naturally just like that? If so, how do we know the products during the exams?