Question

In: Chemistry

Given the following information about Fe in aqueous solutions, what will be the ratio of (Fe(OH)2+)...

Given the following information about Fe in aqueous solutions, what will be the ratio of (Fe(OH)₂⁺) to (Fe(OH)₃⁰) in solution at pH 6.0, 6.5, 7.0, 7.5, 8.0, 8.5?

Fe³⁺ + 2H₂O = Fe(OH)₂⁺ +2H⁺ logK = -5.7

Fe³⁺ + 3H₂O = Fe(OH)₃⁰ + 3H⁺ logK = -13.1

Solutions

Expert Solution

Fe³⁺ + 2H₂O = Fe(OH)₂⁺ +2H⁺ logK = -5.7

K = [Fe(OH)₂⁺ ][H⁺ ]^2/[Fe³⁺ ] k = 10^(-5.7)

[Fe(OH)₂⁺ ] = K[Fe³⁺ ] / [H⁺ ]^2

Fe³⁺ + 3H₂O = Fe(OH)₃⁰ + 3H⁺ logK1 = -13.1

K1 = [ Fe(OH)₃⁰ ][H⁺ ]^3/[Fe³⁺ ] k1 = 10^(-13.1)

[ Fe(OH)₃⁰ ] = K1[Fe³⁺ ]/[H⁺ ]^3

therefore

[Fe(OH)₂⁺ ]/[ Fe(OH)₃⁰ ] = K [H⁺ ]/ K1

at pH = 6 [H+] = 10^(-6)

[Fe(OH)₂⁺ ]/[ Fe(OH)₃⁰ ] = (10^(-5.7)*10^(-6))/ (10^(-13.1))

[Fe(OH)₂⁺ ]/[ Fe(OH)₃⁰ ] = 25.12

at pH = 6.5

[Fe(OH)₂⁺ ]/[ Fe(OH)₃⁰ ] = (10^(-5.7)*10^(-6.5))/ (10^(-13.1))

[Fe(OH)₂⁺ ]/[ Fe(OH)₃⁰ ] = 7.94

At pH = 7.0

[Fe(OH)₂⁺ ]/[ Fe(OH)₃⁰ ] = (10^(-5.7)*10^(-7))/ (10^(-13.1))

[Fe(OH)₂⁺ ]/[ Fe(OH)₃⁰ ] = 2.511

at pH= 7.5

[Fe(OH)₂⁺ ]/[ Fe(OH)₃⁰ ] = (10^(-5.7)*10^(-7.5))/ (10^(-13.1))

[Fe(OH)₂⁺ ]/[ Fe(OH)₃⁰ ] = 0.794

at pH = 8

[Fe(OH)₂⁺ ]/[ Fe(OH)₃⁰ ] = (10^(-5.7)*10^(-8))/ (10^(-13.1))

[Fe(OH)₂⁺ ]/[ Fe(OH)₃⁰ ] = 0.2511

at pH = 8.5

[Fe(OH)₂⁺ ]/[ Fe(OH)₃⁰ ] = (10^(-5.7)*10^(-8.5))/ (10^(-13.1))

[Fe(OH)₂⁺ ]/[ Fe(OH)₃⁰ ] = 0.0794

queen_honey_blossom answered 2 months ago

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