Starting with 11.5 ml of 3.40 × 10−2 M BaCl2?

Question

how many grams of ZnSO4 can be added to the solution before BaSO4 begins to precipitate ?

Answer 1

Ksp for BaSO4 is 1.1 * 10^-10, so the [SO4(2-)] cannot be greater than 3.24 * 10^-9 M.

In 11.5 mL of solution, that is 3.72 * 10^-11 moles, or 6.01 * 10^-9 grams of ZnSO4.