Question

an aqueous solution contains 0.010M br and 0.010 M I. If AG+ is added until agbr(s) just begins to precipitate. what are the concentrations of ag and I? ksp of agbr = 5.4E-13, ksp of agi = 8.5E-17?

Answer 1

Ksp of AgBr = 5.4 x 10^-13

AgBr --------------> Ag+ + Br-

                               Ag+      0.01

Ksp = [Ag+][0.01]

5.4 x 10^-13 = [Ag+][0.01]

[Ag+] = 5.4 x 10^-11 M

Ksp of AgI = 8.5 x 10^-17

AgI   -----------------> Ag+ + I-

                                  Ag+    0.01

Ksp = [Ag+][0.01]

8.5 x 10^-17 = [Ag+][0.01]

[Ag+] = 8.5 x 10^-15 M

here

[Ag+] = 5.4 x 10^-11 M

[I-] = Ksp / [Ag+] = 8.5 x 10^-17 / 5.4 x 10^-11

[I-] = 1.57 x 10^-6 M