Textbook 6D.11 e,f

[MaiVyDang2I]

We're supposed to write the aqueous solution for e) AlCl₃ and f) Cu(NO₃)₂. I was able to identify that both are acidic but I don't know how to write the equation for them. For e), I don't understand why the answer key says they start with Al(H₂O)₆³⁺ instead of AlCl₃.

[Rachel Fox - 3F]

For e and f, Al and Cu are the ions that are going to be interacting with water. Al and Cu both form coordination complexes in water with water being the ligand for each. This is why the answer key starts with Al(H2O)6+3 and Cu(H2O)6+2 because the cation and anion in an aqueous solution will disassociate and the Al and Cu will form coordination complexes with the water. Based on this and the fact that the H2O outside the coordination sphere will be protonated to become H3O+ (which is acidic, making the pH < 7), we can write out the chemical equations:
Al(H2O)6 3+(aq) + H2O(l) <-> Al(H2O)5OH 2+(aq) + H3O+(aq)
Cu(H2O)6 2+(aq) + H2O(l) <-> Cu(H2O)5OH+(aq) + H3O+(aq)