The nickel(II) ion is commonly dissolved in solution using nickel(II) nitrate hexahydrate, Ni(NO3)2.6H2O. The nickel(II) ion precipitates as Ni(OH)2(s) with a Ksp value of 6 x 10-16. Calculate the molar solubility of nickel(II) in a solution with a pH of 10.00
Ni(OH)₂ ⇄ Ni⁺² + 2 OH⁻ Ksp = [Ni⁺²][OH⁻]² = S (2S)² = 4S³ where S is molar solubility. at pH = 10 [H⁺] = 10⁻¹⁰ [H⁺][OH⁻] = 10⁻¹⁴ so [OH⁻] = 10⁻⁴ M Ksp = S [10⁻⁴ + 2S]² Ksp is very small so the molar solubility of OH⁻ will be very small so (10⁻⁴ + 2S) is about 10⁻⁴ so Ksp = S x 10⁻⁸ S = [tex] \frac{6 x 10^{-16} }{10^{-8} } [/tex] = 6 x 10⁻⁸ M
