the reaction that should be followed is
Na2SO4 + Ca(NO3)2 --> CaSO4 + 2NaNO3
first calculate the limiting reactant
mol Na2SO4 = 0.075 L (1.54×10−2 mol / L) = 1.155x10-3 mol
mol Ca(NO3)2 = 0.075 L (1.22×10−2 mol / L) = 9.15x10-4 mol
so the limiting reactant is the Ca(NO3)2
so all of the Ca2+ will be precipitated, percentage unprecipitated = 0.00 %