What is the approximate concentration of free Fe³⁺(aq)ion in a solution prepared by mixing equal volumes of 0.06 M Fe³⁺(aq)and 4.0 M F^-(aq)solutions? [The net formation constant for FeF₅(H₂O)^2- is 2.0 × 10¹⁵.]

Question

Quizplus · Accepted Answer

The balanced chemical equation for the reaction between FeS1U1P13+S1S1P0(aq) ion and FS1U1P1-S1S1P0(aq) ion is:

FeS1U1P13+S1S1P0(aq) + FS1U1P1-S1S1P0(aq) -> FeFS1U1B15S1U1B0(HS1U1B12S1U1B0O)S1U1P12-S1S1P0 + S1U1P12-S1S1P0

The net formation constant for the reaction is 2.0 × 10S1U1P115S1S1P0.

Let the concentration of FeS1U1P13+S1S1P0(aq) ion be x. Then, the initial concentrations of FeS1U1P13+S1S1P0(aq) ion and FS1U1P1-S1S1P0(aq) ion are both 0.03 M (since the volumes are equal and the concentrations are halved).

Using the equilibrium constant expression:

Kf = [FeFS1U1B15S1U1B0(HS1U1B12S1U1B0O)S1U1P12-S1S1P0][S1U1P12-S1S1P0] / [FeS1U1P13+S1S1P0][FS1U1P1-S1S1P0]

2.0 × 10S1U1P115S1S1P0 = [(x)(x)] / [(0.03 - x)(0.03 - x)]

Since x << 0.03, we can assume that 0.03 - x ≈ 0.03.

2.0 × 10S1U1P115S1S1P0 ≈ xS1U1P12-2 / (0.03)S1U1P12-2

x ≈ 6.9 × 10S1U1P1-19S1S1P0 M

Therefore, the approximate concentration of free FeS1U1P13+S1S1P0(aq) ion is 6.9 × 10S1U1P1-19S1S1P0 M. The best choice is C.

What Is the Approximate Concentration of Free Fe3+(aq)ion in a Solution

What Is the Approximate Concentration of Free Fe³⁺(aq)ion in a Solution