Amphoteric substances metal hydroxide solubility

Some metal oxides and hydroxides that are relatively insoluble in water dissolve in strongly acidic and strongly basic solutions. These substances, called amphoteric oxides and amphoteric hydroxides, are soluble in strong adds and bases because they themselves are capable of behaving as either an acid or base. Examples of amphoteric substances include the oxides and hydroxides of Al, Cr, Zn, and Sn. ... 

If you recall from Chapter 14, the term amphoteric refers to a substance that can act as either an acid or a base. Many metal oxides and hydroxides that are fairly insoluble in water are quite soluble in strongly acidic and basic solutions. These materials can dissolve in both acids and bases because they are amphoteric—that is, they are capable of acting like acids or bases. One example is zinc hydroxide, Zn(OH)2. Zinc hydroxide is quite insoluble in water (Ksp = 3 X 10 17). However, if placed in a strong acid, the hydroxide ion reacts with the hydrogen ion in the acid in the following way ... 

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