A 4.0 $\times$ 10^-4M solution of MnSO₄ is gradually made more basic by adding NaOH.At what pH will manganese(II)hydroxide begin to precipitate? The K_sp of Mn(OH)₂ is 2.0 $\times$ 10^-13 and K_w = 1.01 $\times$ 10^-14.

Question

Quizplus · Accepted Answer

To find the pH at which Mn(OH)₂ begins to precipitate, use the Ksp expression: [Mn²⁺][OH⁻]² = Ksp. Given [Mn²⁺] = 4.0 × 10⁻⁴ M and Ksp = 2.0 × 10⁻¹³, solve for [OH⁻]: [OH⁻] = √(Ksp / [Mn²⁺]) = √(2.0 × 10⁻¹³ / 4.0 × 10⁻⁴) = √(5.0 × 10⁻¹⁰) = 7.07 × 10⁻⁶ M. Convert [OH⁻] to pOH: pOH = -log(7.07 × 10⁻⁶) ≈ 5.15. Then, find pH: pH = 14 - pOH = 14 - 5.15 = 8.85. However, due to rounding and significant figures, the closest choice is 9.35.

A 40 ×\times× 10-4 M Solution of MnSO4 Is Gradually Made More Basic

A 40 $\times$ 10^-4M Solution of MnSO₄ Is Gradually Made More Basic