Textbook Question 6D-15 (b)

[Marta Olson 3F]

Hi,

I'm working on textbook problem 6D-15, part B, which asks about finding the pH given 0.055 M of AlCl3. I'm having a hard time writing out the equation for this problem. Looking at the answer key, it shows that it is Al(H2O)6 3+(aq) + H2O(l) --> H3O+(aq) + Al(H2O)5OH2+(aq)

I'm really confused about how to get that from the given AlCl3. Can someone walk me through it? Thanks!

[Abeni Liu 2B]

AlCl3 is composed of the ions Al3+ and 3Cl-. Since Cl- is a spectator ion, it does not show up in the reaction. Al3+ acts as an acid and donates a proton to water. (Generally cations act as acids). As for why there is 6 H2O, I'm not too sure but the textbook does provide a table and explains it. Hope this helps!