Question

A generic salt, AB2, has a molar mass of 317 g/mol and a solubility of 4.30 g/L at 25 °C. What is the Ksp of this salt at 25 °C?

Answer 1

mass solubility of salt = 4.30 g/L

molar solubility of salt = (mass solubility of salt) / (molar mass of salt)

molar solubility of salt = (4.30 g/L) / (317 g/mol)

molar solubility of salt = 0.0136 M

Ksp AB₂ = [A][2B]²

Ksp AB₂ = (s) * (2s)²

Ksp AB₂ = (s) * (4s²)

Ksp AB₂ = 4s³

where s = solubility

Ksp AB₂ = 4 * (0.0136 M)³

Ksp AB₂ = 9.98 x 10^-6