Question

FeCl3(s) is often added as a flocculant to water in treatment plants. For the problems below, assume that ferrihydrite, Fe(OH)3(s),
is the only solid that forms.

(b) Determine the pH and dissolved iron concentration if 10−4 M FeCl3 were
added to pure water.

Answer 1

Answer on question #59193 - Chemistry - Inorganic Chemistry

Question:

FeCl3(s) is often added as a flocculant to water in treatment plants. For the problems below, assume that ferrihydrite, Fe(OH)3(s), is the only solid that forms.

Determine the pH and dissolved iron concentration if $10^{-4}$ M $\mathrm{FeCl}_3$ were added to pure water.

Solution:

The equation of hydrolysis of $\mathrm{FeCl}_3$ :

$$\mathrm{FeCl}_3 + \mathrm{H}_2\mathrm{O} = \mathrm{Fe(OH)Cl}_2 + \mathrm{HCl}$$

The hydrolysis constant is:

$$K_h = K(H_2O)/K_b(Fe(OH)^2+) = 10^{-14}/1.82*10^{-11} = 5.49*10^{-4}$$

The concentration of $\mathsf{H}^+$ is $2.34*10^{-4}$ M

The pH of solution is 3.63

The total concentration of dissolved iron is $10^{-4}$ M

Answer:

The pH of solution is 3.63

The total concentration of dissolved iron is $10^{-4}$ M

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