how many NaOH are needed to to react with 98.1 mol AlO3

Dear marie,

I guess there is no AlO3 existing
So do you actually mean aluminium oxide
(Al2O3)
The balanced equation is
3OH- + AL3+ -------> Al(OH)3
mol of aluminium oxide needed= 98.1

as 1 mole of aluminium oxide required 3 moles of sodium hydroxide to react with

mol of sodium hydroxide= 98.1X3
= 294.3

number of grams of NaOH needed=
294.3x( 23+ 16 +1)
=11772grams