Question

For which of the following mixtures will Ag2SO4(s) precipitate?

150.0 mL of 0.10 M Na2SO4(aq) and 5.0 mL of 0.20 M AgNO3(aq)

150.0 mL of 0.10 M Na2SO4(aq) and 5.0 mL of 0.30 M AgNO3(aq)

150.0 mL of 0.10 M Na2SO4(aq) and 5.0 mL of 0.40 M AgNO3(aq)

150.0 mL of 0.10 M Na2SO4(aq) and 5.0 mL of 0.50 M AgNO3(aq)

Help?? I know I have to use Qsp equation, but I feel like I'm stil not getting the correct answer

Answer 1

Calculate (Ag^+) and (SO4^2-), substitute into Ksp expression. That is Qsp.
If Qsp > Ksp a ppt will occur. If Qsp < Ksp, no ppt will occur.
For example, a)
(SO4^2-) = 150.0 x 0.10/155.0)= 0.0968M
(Ag^+) = 5.0 x 0.2/155.0 = 0.00645M
(0.00645)^2(0.0968) = 4.03E-6 which is smaller than Ksp = 1.20E-5; therefore, no ppt of Ag2SO4 will occur.