H2SO4 The balanced reaction between Al(OH)3 and H2SO4 is 3 H2SO4 + 2Al(OH)3 ==> Al2(SO4)3 + 6 H2O So that indicates that you need 3 H2SO4 molecules for every 2 Al(OH)3 molecules. So you need more H2SO4 than you need Al(OH)3. Since you have the same number of moles of each reactant, that means that the limiting reactant is H2SO4