1.20

a)
Al_2O_3\left(s\right)+2NaOH\left(aq\right)+H_2O\left(l\right)\rightarrow2NaAl\left(OH\right)_4\left(aq\right)
b)
Al_2O_3\left(s\right)+6HCl\left(aq\right)\rightarrow2AlCl_3+3H_2O