Question

Sodium sulfate is slowly added to a solution containing 0.0500 m ca2 (aq and 0.0390 m ag (aq. what will be the concentration of ca2 (aq when ag2so4(s begins to precipitate?

Answer 1

balanced equation:
CaSO4(aq) + AgNO3(aq) -> Ag2SO4(s) + Ca(NO3)2(aq)

Twice the amount of silver is needed than SO4 in order to precipitate. Silver would be the limiting reagent (from AgNO3).
Find the leftover concentration of CaSO4 by subtracting the amount that reacted with the silver.

∴[CaSO4]=[Ca^2+]=0.0500M-0.0390M= 0.0110 M