(5.a) NO PRECIPITATION WILL OCCUR
CaCl2(aq) + Na2SO4(aq) ---> CaSO4(s) + 2NaCl(aq)
Ca+2 + 2Cl- + 2Na+ +SO4-2---> CaSO4 + 2Na+ + 2Cl-
Ca+2 + SO4-2 ---> CaSO4
Since the Ksp = [Ca+2][SO4-2] = 2.4 x 10-5 M, whenever the product (Q) of the concentrations exceeds the Ksp, precipitation should occur.
Q = [Ca+2][SO4-2]
Q = (0.00005 moles/0.100L ) x (0.0005 moles/0.100 L)
Note: By mixing the solution you have to use total volume and the concentrations are lowered (dilution).
Q = [ 5 x10-4] [5 x 10-3]
Q = 2.5 x 10-6 M
Since the value of Q is less than Ksp then no precipitate will form.