NiS has a Ksp of 4.0 x 10^-20. What is the solubility of NiS in mol/L?

• A. 1.5 x 10^-6 M
• B. 7.3 x 10^-8 M
• C. 2.0 x 10^-10 M
• D. 4.5 x 10^-9 M

Answer: (B)

Verified step by step guidance

1. Start by writing the balanced dissolution equation for NiS: NiS(s) ⇌ Ni²⁺(aq) + S²⁻(aq).
2. Express the solubility product constant (Ksp) for NiS in terms of the concentrations of the ions: Ksp = [Ni²⁺][S²⁻].
3. Assume the solubility of NiS is 's' mol/L. Therefore, [Ni²⁺] = s and [S²⁻] = s, since one mole of NiS produces one mole of Ni²⁺ and one mole of S²⁻.
4. Substitute the concentrations into the Ksp expression: Ksp = s × s = s².
5. Set the Ksp value equal to the expression and solve for 's': 4.0 × 10⁻²⁰ = s². Take the square root of both sides to find the solubility 's'.