Answer
Please see the work below.
Work Step by Step
a. Since the PH increases, a precipitate of $Al(OH)_3$ forms .
b. The balanced chemical equations of the reactions are
$Al^{+3}+3OH^{-}\rightarrow Al(OH)_3$
$Al(OH)_3+OH^{-}\rightarrow Al(OH)_4^{-}$
