12.65 (e) and (f)

[Omer Lavian 2K]

Determine whether an aqueous solution of each of the
following salts has a pH equal to, greater than, or less than 7.
If pH & 7 or pH ' 7, write a chemical equation to justify your
answer. (a) NH4Br; (b) Na2CO3; (c) KF; (d) KBr; (e) AlCl3;
(f) Cu(NO3)2.

I understand that Al3+ and Cu2+ are small, highly charged cations that can protonate an H2O molecule. I'm just confused about the equation, which shows the hydrates of the cations: Al(H2O)63+ and Cu(H2O)62+. When dealing with metal hydrates in an aqueous solution, are water molecules and metal ions combing to make an octahedral TM complex, or is there another reason that the metal hydrates are written with 6 H2O molecules?

[Belicia Tang 1B]

I have the same question. I'm not sure why exactly there are 6 water molecules surrounding the cation. Also, is the charge of each individual water molecule neutral? Or does it take on the charge of the entire complex (so in part e, the charge of the complex is 3+, so is each water molecule also 3+?)

[Omer Lavian 2K]

I mean water is neutral, so I assume the charge corresponds to the ion and thus the entire complex.

[isabelle ruedisueli 1j]

I have a similar question for number 12.69 part B. It says calculate the pH of 0.055M AlCl3 and then the reaction, in the solution manual, has the reaction as Al(h20)6^3+. Why is the Cl gone? and Are all metals going to bond with water molecules?
Thanks

[Natalie Rotstein 3J]

I was wondering this as well, and also, if which metal ions form water complexes and how they do it is something we would need to know for the final or if that information would be given to us if there was a question about it?

[Sana Nagori 2H]

I don't know about the hydrates part but for determining the pH, the positive charge on the TM cations would want to bond with the partially negative oxygen atom of water thus weakening a O-H bond and releasing a H+ so that is why the pH<7