MCQ Detailed View

Solubility of ionic compounds in water depends on the balance between lattice energy and hydration energy. Sulfates of alkaline earth metals (Group 2) show varying solubilities due to differences in these two factors.

Lattice energy is the energy released when ions form a solid lattice. A high lattice energy makes a salt less soluble because more energy is required to break the ionic lattice. Hydration energy is the energy released when ions are solvated by water molecules. A high hydration energy increases solubility, as it helps overcome lattice energy.

Among the given compounds:

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  BaSO₄ (Barium sulfate): Very low solubility in water because Ba²⁺ is large and lattice energy dominates.

  
  


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  SrSO₄ (Strontium sulfate): Slightly more soluble than BaSO₄ but still poorly soluble.

  
  


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  CaSO₄ (Calcium sulfate): Moderately soluble; lattice energy is lower than SrSO₄ but still limits solubility.

  
  


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  MgSO₄ (Magnesium sulfate): Highly soluble because Mg²⁺ is small with high charge density, leading to very high hydration energy that overcomes lattice energy.

  
  

The solubility trend of Group 2 sulfates in water is:

$$\text{MgSO₄ > CaSO₄ > SrSO₄ > BaSO₄}$$

Magnesium sulfate dissolves readily in water to give Mg²⁺ and SO₄²⁻ ions, making it useful in medicine, agriculture, and industry. Understanding this trend helps predict reactivity, precipitation reactions, and industrial applications of sulfates.

Therefore, among the given options, MgSO₄ is the most soluble in water.