Ferric Hydroxide, Fe(OH)3, is an insoluble salt with a solubility of 10^-39.

1) What is the maximum concentration of ferric hydroxide that can dissolve?
2) Using Le Chatalier's Principle, explain why iron (III) solutions are more soluble in acidic solution.

In this case, the OH- will predominate in the solution, adding acid will cause H+ ions to convert the OH- to water, LeChatalier predicts more will dissolve to undo that rduction in OH-

Thank you bobpursley..how can I determine the max concentration for Fe(OH)3 that will dissolve though?

Wouldn't it make sense that you need the pH of the solution to determine the solubility. You don't have a pH or the amount of the solute. And 10^-39 what

That's why I was confused, it just states that the Fe(OH)3 has a solubility product of 10^-39. Any ideas?

Fe(OH)3 <=> Fe^+3 + 3OH^-

Ksp = [Fe^+3][OH^-]^3
Ksp = (x)(3x)^3 = 27x^4
=> x = Solubility of Fe(OH)^3
---- = (Ksp/27)^1/4
---- = (1x10^-39/27)^1/4
---- = 7.8x10^11 Molar
[OH^-] = 3(7.8x10^-11)M = 2.4x10^-10M
=> pOH = -log[OH^-] = -log(2.4x10^-10) = 9.63
pH + pOH = 14 => pH = 14 - 9.63 = 4.37

Fe(OH)3 <=> Fe^+3 + 3OH^-
-------------------------
^

Adding H+ reacts with OH^- => HOH and leaves the product side of equilibrium needing OH^-. This causes more Fe(OH)3 to ionize to replace OH^- until all additional H^+ is converted to HOH => increasing solubility OF Fe(OH)3.

To find the maximum concentration of ferric hydroxide that can dissolve, we can use the solubility product constant (Ksp). The Ksp expression for ferric hydroxide is as follows:

Ksp = [Fe3+][OH-]^3

Given that the solubility is 10^-39, we can assume that the concentrations of [Fe3+] and [OH-] are also 10^-39. Plugging these values into the Ksp expression:

Ksp = (10^-39)(10^-39)^3
Ksp = (10^-39)(10^-117)
Ksp = 10^-156

So, the maximum concentration of ferric hydroxide that can dissolve is 10^-156.

Now, moving on to the explanation of why iron (III) solutions are more soluble in acidic solutions using Le Châtelier's Principle.

Le Châtelier's Principle states that a system at equilibrium, when subjected to a stress, will adjust itself to minimize the effect of that stress and regain equilibrium. In the case of ferric hydroxide, increasing the acidity of the solution acts as a stress on the equilibrium system.

When ferric hydroxide dissolves, it undergoes the following reaction:

Fe(OH)3(s) ⇌ Fe3+(aq) + 3OH-(aq)

By Le Châtelier's Principle, if more acid is added to the solution, the concentration of H+ ions will increase. This increased concentration of H+ ions will shift the equilibrium to the left in order to consume those H+ ions, minimizing the effect of the additional acid.

By shifting the equilibrium to the left, more solid ferric hydroxide (Fe(OH)3) will dissolve to produce more Fe3+ ions and OH- ions. Thus, iron (III) solutions are more soluble in acidic solutions because the increased concentration of H+ ions in the acidic solution helps to dissolve more ferric hydroxide through the shifting of the equilibrium.