Question

The solubility of magnesium oxalate, MgC₂O₄, in water is 0.0093g/L. Calculate K_sp. Use ICE.

Answer 1

Solubility is the meximum amount of a substance dissolved per liter of the solvent.

MgC₂O₄ upon dissolution in water forms following ions

MgC₂O₄ <---------> Mg²⁺ + C₂O₄^2-

Ksp = [Mg²⁺] [C₂O₄^2-]

[Mg²⁺] and [C₂O₄^2-] are the molar concentration of Mg²⁺ and C₂O₄^2-

SOLUBILITY = 0.0093g/L, It means 0.0093 g of MgC₂O₄ dissolves in 1L of water, Hence amount of [Mg²⁺] and [C₂O₄^2-] ions in solution = 0.0093g/L

Convert the solubility from g/L to moles /L

No. of moles of  MgC₂O₄ = Mass dissolved / Molar mass

= 0.0093g / 112.32g/mol = 8.27 X 10^-5 mol/L

Ksp = [8.27 X 10^-5 ] [8.27 X 10^-5 ] = 6.84 X 10^-9