Question

When iron(II) hydroxide is dissolved in water the following solubility equilibrium is estabished: ________ Fe(OH)2 ⇌ _________ Fe2+ + _________ OH-
With the following solubility product expression Ksp = ({Fe(OH)2}^ _________ ) ({Fe2+}^ __________ ) ({OH-}^ __________ )

Note: For this question { } indicate concentration.

Answer 1

First, let us define the equilibrium constant for any species:

The equilibrium constant will relate product and reactants distribution. It is similar to a ratio

The equilibrium is given by

rReactants -> pProducts

Keq = [products]^p / [reactants]^r

For a specific case:

aA + bB = cC + dD

Keq = [C]^c * [D]^d / ([A]^a * [B]^b)

Where Keq is constant at a given temperature, i.e. it is dependant on Temperature only

If Keq > 1, this favours products, since this relates to a higher amount of C + D

If Keq < 1, this favours reactants, since this relates to a higher amount of A + B

If Keq = 1, this is in equilibrium, therefore, none is favoured, both are in similar ratios

For Ksp:

Ksp = [Fe2+][OH-]^2 / [Fe(OH)2(s)]

then, form previous data;

recall that the solid has an activity of 1

Ksp = [Fe2+][OH-]^2 / [Fe(OH)2(s)]

Ksp = [Fe2+][OH-]^2 /1

Ksp = [Fe2+][OH-]^2