[Tangera]

Hello!

My question is why does aluminium chloride give an acidic solution when dissolved in water? I am aware that AlCl₃ is a covalent molecule that ionizes in water into Al³⁺ and Cl^-...does this happen to have anything to do with it giving an acidic solution in water?? My guess is that H₃O+ ions may be formed as well, but why then, will H₃O+ ions give an acidic solution?

Thank you for helping!

[Borek]

What form does the Al³⁺ cation take in water?

[manyuen_wong]

Hello!

My question is why does aluminium chloride give an acidic solution when dissolved in water? I am aware that AlCl₃ is a covalent molecule that ionizes in water into Al³⁺ and Cl^-...does this happen to have anything to do with it giving an acidic solution in water?? My guess is that H₃O+ ions may be formed as well, but why then, will H₃O+ ions give an acidic solution?

Thank you for helping!

Al³⁺, having a high charge/surface area ratio charge density, polarizes the water ligands and ejects out H⁺ ions.
As a result of polarization by Al³⁺, there is a drift of electron density towards Al³⁺ and this weakens the OH bonds

[cliverlong]

Hello!

My question is why does aluminium chloride give an acidic solution when dissolved in water?

I am aware that AlCl₃ is a covalent molecule that ionizes in water into Al³⁺ and Cl^-

My textbook, Facer, A2 Chemistry and the following link

http://www.chemguide.co.uk/inorganic/period3/chlorides.html#top

states that anhydrous Aluminium Chloride is hydrolysed by water, through a few intermediates, ending up producing H₃O⁺ and hence the acidity, not the simple ionisation that you have written.

I am aware that AlCl₃ is a covalent molecule

again Chemguide gives more detailed information on the structure of Aluminium (III) Chloride and shows, depending on temperature, the dative bonds, not just covalent bonds, leading to a molecular formula Al₂Cl₆

I am aware that AlCl₃ is a covalent molecule

Facer states that adding water to hydrated Aluminium Chloride , deprotonates the AlCl₃ H₂O complex producing H₃O⁺ and hence the acidity.

Clive