Answer:
I would go for number 5 . It sounds more logical to me.
Answer:
0.4590
Explanation:
How the refractive index of the hexane + toluene mixture varies linearly with mole fraction, it means that the mole fraction is the fraction that each pure index contribute for the mixture index, so, calling <em>xh</em> the mole fraction of hexane and <em>xt</em> the mole fraction of toluene:
1.375xh + 1.497xt = 1.441
And, xh + xt = 1 (because there are only hexane and toluene in the mixture), so xt = 1- xh
1.375xh + 1.497(1-xh) = 1.441
1.375xh + 1.497 - 1.497xh = 1.441
-0.122xh = -0.056
xh = -0.056/(-0.122)
xh = 0.4590
1- getting the molar solubility:
We have the compound Fe(OH)2. It dissociates based on the following equation:
Fe(OH)₂ <======> Fe2+ + 2OH-
we can note that the concentration of hydroxide is twice that of iron
Therefore:
Assuming that the molar solubility is x,
Ksp = x * (2x)²
4.87 * 10^-17 = 4x³
x³ = 1.2175 * 10^-17
x = 2.3 * 10^-6 mole / liter
In case you want the solubility in grams / liter:
2- getting the molar mass of Fe(OH)2:
From the periodic table:
mass of Fe = 55.8 grams
mass of O = 16 grams
mass of H = 1 gram
Therefore:
molar mass of Fe(OH)2 = 55.8 + 2(16+1) = 89.8 grams
3- getting the solubility in grams / liter:
solubility i grams / liter = solubility in moles / liter * molar mass
solubility in grams / liter = 2.3 * 10^-6 * 89.8
solubility = 2.0654 * 10^-4 gram / liter
Hope this helps :)