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
