The K_sp of Fe(OH)₃(s)is 3 × 10−³⁹.What concentration of Fe³⁺ can exist in solution at pH 3.0?

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The dissociation reaction of Fe(OH)₃(s) is: Fe(OH)₃(s) ⇌ Fe³⁺(aq) + OH−(aq) The equilibrium constant for this reaction is the solubility product constant, K_sp, which is given as 3 × 10−³⁹. At pH 3.0, the hydroxide ion concentration is 10−¹¹ M. We can assume that the concentration of Fe³⁺ in solution is much less than the hydroxide ion concentration, so we can neglect the contribution of the Fe³⁺ to the overall pH. Therefore, using the equilibrium expression for the dissociation reaction, we get: K_sp = [Fe³⁺][OH−] 3 × 10−³⁹ = [Fe³⁺][10−¹¹] Solving for [Fe³⁺], we get: [Fe³⁺] = (3 × 10−³⁹) / (10−¹¹) [Fe³⁺] = 3 × 10−²⁸ M Therefore, the concentration of Fe³⁺ that can exist in solution at pH 3.0 is 3 × 10−²⁸ M, which corresponds to choice B.

The Ksp of Fe(OH)3(s)is 3 × 10−39

The K_sp of Fe(OH)₃(s)is 3 × 10−³⁹