A 6.6 × 10–4 M solution of MnSO4 is gradually made more basic by adding NaOH. At what pH will manganese(II) hydroxide begin to precipitate? For Mn(OH)2, Ksp = 2.0 × 10–13.

Question

A 6.6 × 10–4 M solution of MnSO4 is gradually made more basic by adding NaOH. At what pH will manganese(II) hydroxide begin to precipitate?  For Mn(OH)2, Ksp = 2.0 × 10–13.

DrBob222 · Answer

(Mn^+2)(OH^-) = 2.0 x 10^-13 Substitute 6.6 x 10^-4 for Mn^+2 in Ksp and solve for OH^-. Convert to pOH, then to pH.