The salt having the least solubility in water is : — Chemical Bonding Chemistry Question

💡 Solution & Explanation

Step 1: Solubility of sulfate salts of group 2 elements (alkaline earth metals) decreases down the group. Step 2: As the cation size increases from Mg^2+ to Ba^2+, the hydration energy decreases much faster than the lattice energy. For BaSO4, the lattice energy dominates and cannot be compensated by the hydration of Ba^2+ and SO4^2- ions. Step 3: Therefore, barium sulfate (BaSO4) is highly insoluble in water (sparingly soluble), having the least solubility among the options, which corresponds to option (d).