Question

Above what Fe2+ concentration will Fe(OH)2 precipitate from a buffer solution that has a pH of 8.79

The ?sp of Fe(OH)2 is 4.87×10−17 M3

Answer 1

Given that, pH = 8.79 Ksp of Fecoh us 4.87X10 17. It us known that, he oper pOH = 14 - PH - 14 - 8.79 1. " O pot = 5.21 Therefore, [OH] = (10)-5:21 at the 6-17 X10-6 c m By Ksp rele beste is Ksp = [Feet] [CH]² 4.87% 1017 = [Feet] [6.17810672 [Fe 2+ ] 4.87 41017 (6.17 x 10672 [[Fe²+] = 1.4x106m Answer: The concentration of Fe 2+ us 1.4x100m.

Answer 2

The pOH and [OH-] are calculated:

pOH = 14 - 8.79 = 5.21

[OH-] = 10 ^ -5.21 = 6.2x10 ^ -6 M

You have the expression of Ksp:

Ksp = [Fe + 2] * [OH -] ^ 2

4.87x10 ^ -17 = [Fe + 2] * (6.2x10 ^ -6) ^ 2

It clears [Fe + 2] = 1.27x10 ^ -6 M

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