Question

How many moles of sodium sulfate, Na2SO4, would need to be added to 1.0 L of 0.055M silver nitrate, AgNO3, to cause silver sulfate, Ag2SO4, to precipitate. The Ksp of Ag2SO4 is 1.4x10-5.

Answer 1

moles of AgNO3 = 1.0 x 0.055 = 0.055

Na2SO4 + 2 AgNO3 -----------------------> Ag2SO4 + 2 NaNO3

1 mol             2 mol

? mol             0.055 mol

1 mol Na2SO4 --------------------> 2 mol AgNO3

x mol Na2SO4 --------------------> 0.055 mol AgNO3

moles of Na2SO4 needed = 1 x 0.055 / 2

                                         = 0.0275

moles of Na2SO4 needed = 0.0275