Strontium sulfate, SrSO4, would be the least soluble in which following solutions?
a) 0.1 M HCl
b) 0.1 M NaF
c) 0.1 M Na2SO4
d) 0.1 M NaOH
e) 0.1 M NaCl
The Correct Answer and Explanation is :
The correct answer is (c) 0.1 M Na₂SO₄.
Explanation:
Strontium sulfate (SrSO₄) is an ionic compound, and its solubility is affected by the presence of common ions in solution. This is due to the common ion effect, which reduces the solubility of a salt when a common ion is added to the solution. The solubility product constant (Ksp) for SrSO₄ is very small, indicating that it is poorly soluble in water.
The solubility of SrSO₄ is governed by the equilibrium: SrSO₄ (s)⇌Sr2+(aq)+SO₄2−(aq)\text{SrSO₄ (s)} \rightleftharpoons \text{Sr}^{2+} (aq) + \text{SO₄}^{2-} (aq)
Now, let’s analyze each solution:
- 0.1 M HCl (a): Hydrochloric acid dissociates into H⁺ and Cl⁻ ions. The chloride ion (Cl⁻) does not share a common ion with SrSO₄, so the solubility of SrSO₄ would not be significantly affected by the presence of HCl. Therefore, SrSO₄ would have moderate solubility in this solution.
- 0.1 M NaF (b): Sodium fluoride dissociates into Na⁺ and F⁻ ions. Neither of these ions is a common ion to SrSO₄. Thus, the solubility of SrSO₄ would not be strongly affected by NaF.
- 0.1 M Na₂SO₄ (c): Sodium sulfate dissociates into Na⁺ and SO₄²⁻ ions. The sulfate ion (SO₄²⁻) is a common ion with SrSO₄. According to the common ion effect, the presence of additional sulfate ions in solution would shift the equilibrium to the left, reducing the solubility of SrSO₄. Hence, SrSO₄ would be the least soluble in this solution.
- 0.1 M NaOH (d): Sodium hydroxide dissociates into Na⁺ and OH⁻ ions. Neither Na⁺ nor OH⁻ ions are common to SrSO₄, so SrSO₄’s solubility would not be greatly affected by NaOH.
- 0.1 M NaCl (e): Sodium chloride dissociates into Na⁺ and Cl⁻ ions. Again, neither of these ions is a common ion to SrSO₄, so its solubility would not be significantly affected by NaCl.
Therefore, the presence of the sulfate ion in 0.1 M Na₂SO₄ will have the greatest effect in reducing the solubility of SrSO₄, making it the least soluble in this solution.