6. Chemical Equilibrium

What is the molar solubility of Fe(OH) ₃ (s) in a solution that is buffered at pH 3.50 at 25°C? The Ksp of Fe(OH)₃ is 6.3 x 10^–38 at 25°C.

Arsenic trisulfide (As₂S₃) occurs naturally as the orange-yellow colored mineral orpiment. As₂S₃ is a highly insoluble substance with a Ksp value of 2.90×10⁻⁷². Calculate the solubility of As₂S₃ in g/100mL. (Molar mass of As₂S₃ = 246.04 g/mol)