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J. W. Hill, R. H. Petrucci, T. W. McCreary, & S. S. Perry General Chemistry 4th edition

Review Question 16.15

Write an equation involving [Al(H2O)6]3+ to account for the fact that aqueous solutions of Al3+ are acidic.




Answer:

This is like any other cation hydrolysis if we separate one water molecule from the others:

[Al(H2O)6]3+ = [(H2O)Al(H2O)5]3+

The red hydrogen atom becomes the hydrogen ion donor in a typical Brønsted–Lowry acid:

[(H2O)Al(H2O)5]3+ (aq) + H2O(l)H3O+(aq) + [Al(H2O)5(OH)]2+(aq)