Aluminum Conjugate

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Jonathan Pai 2I
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Joined: Fri Sep 28, 2018 12:27 am

Aluminum Conjugate

Postby Jonathan Pai 2I » Mon Jan 21, 2019 2:21 pm

In 6D15, why does the AlCl3 become Al(H2O)^6 in the chemical equation, why doesn't it just become Al^3+, and why would it get 6 water molecules? And where was the Ka value provided? Thanks.

Jayasuriya Senthilvelan 4I
Posts: 31
Joined: Thu Jan 10, 2019 12:17 am

Re: Aluminum Conjugate

Postby Jayasuriya Senthilvelan 4I » Mon Jan 21, 2019 2:36 pm

So, the AlCl3 becomes Al3+ and 3Cl-. The Cl- is obviously unreactive. But, the Al3+ forms coordinate covalent bonds (I believe) with water. The number of waters can't be logically determined. The same thing happens for Fe3+.

So we have: (Al(H2O))3+. But, what can happen is that another water molecule (other than the six that are surrounding the Al) will come and grab a H+ ion from one of the H2O surrounding the Al. When this happens, H3O+ is formed, and the solution is acidic.

(Al(H2O)6)3+ + H2O --> (Al(H2O)5(OH))2+ + H3O+

The ka value for this reaction should be found in a table in your book. Check the section titled ph of salt solutions.

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