You want to run an experiment using Fe(OH)_3 to confirm the literature data foun
ID: 1063106 • Letter: Y
Question
You want to run an experiment using Fe(OH)_3 to confirm the literature data found for this compound. Before you do the experiment you calculate what the literature says you should have at two different temperatures. Show all calculations and solve for the following values with correct units and significant figures. K_sp (25.0 degree C) = 2.790 times 10^-39 K_sp (50.0 degree C) = 4.653 times 10^-38 pH (25.0 degree C) = pH (50.0 degree C) = Delta G (25.0 degree C) = Delta G (50.0 degree C) = Delta S degree = Delta H degree =Explanation / Answer
Fe(OH)3 <-> Fe+3 + 3OH-
Ksp = [Fe+3][OH-]^3
2.79*10^-39 = (S)(3S)^3
27S^4 = 2.79*10^-39
S = (2.79*10^-39)/27)^1/4)
S = 1.00823*10^-10 M
[OH-] = 3S = 3*10^-10 M
pOH = -log( 3*10^-10 = 9.5228
pH = 14-9.5228
pH = 4.4772
for pH at 50°C
use Ksp at 50°C
Ksp = [Fe+3][OH-]^3
4.653*10^-38 = (S)(3S)^3
27S^4 =4.653*10^-38
S = ((4.653*10^-38)/27)^(1/4)
S = 2.0374*10^-10 M
[OH-] = 3S = 3*2.0374*10^-10 M = 6.11*10^-10
pOH = -log( 6.11*10^-10) = 9.21
pH = 14-9.21 = 4.79
c)
dG = -RT*ln(K)
dG = -8.314*298*ln(2.79*10^-39) = 219945.90 J/mol = 219.94 kJ/mol
d)
dG = -RT*ln(K)
dG = -8.314*(273+50)*ln(4.653*10^-38) = 230840.81 J/mol = 230.84 kJ/mol