The balanced chemical reaction would be written as:
Hg(ClO4)2 + Na2SO4 → 2 NaClO4 + HgSO4(s)
We are given the amounts of both of the reactants to be used for the reaction. We use these values as the starting point of the calculations.
18.96 g Hg(ClO4)2 ( 1 mol / 399.4912 g ) = 0.0475 mol Hg(ClO4)2
6.256 g Na2SO4 ( 1 mol / 142.04 g ) = 0.0440 mol Na2SO4
We have a 1 is to 1 ratio of the reactants. Thus, the limiting reactant would be Na2SO4. We use this value for calculating the amount of products in the reaction.
0.0440 mol Na2SO4 ( 1 mol HgSO4 / 1 mol Na2SO4 ) ( 296.65 g / mol ) = 13.06 g HgSO4
mass of excess reactant = (0.0475 - 0.0440) mol ( 399.4912 g / 1 mol ) = 172.180 g Hg(ClO4)2
