Question

Are all hydroxides basic? What makes a base basic, and an acid acidic?

Answer 1

Both `H_2SO_4` and `HNO_3` contain hydroxides....i.e. `""^(-)O-stackrel+N=O(OH)`, and `(HO)_2S(=O)_2`

Explanation:

Both `H_2SO_4` and `HNO_3` contain hydroxides....and yet these are STRONG acids....

And an acid is typically the hydroxide of a non-metal, whereas a base is typically the hydroxide of a metal.

Non-metals, from the right hand side of the Periodic Table as we face it, TEND to polarize the electron density towards themselves, thereby weakening the `O-H` bond of their HYDROXIDES. On the other hand, metals, tend to have their electron density REMOVED by the oxygen centre....

Here we got `B(OH)_3`...and the oxygen TENDS to polarize the electron density of the `O-H` bond TOWARDS itself...

`(stackrel(delta+)H-stackrel(delta-)O-)_3B`

....and this the `H-O` is WEAKENED somewhat....`pK_a=9.24`