Solubility of Hydroxides in Water:

The solubility of hydroxides in water depends on the strength of the metal-hydroxide bond. The more the bond is strong, the less soluble the hydroxide will be in water. Therefore, the solubility order of hydroxides is:

Ba(OH)2 > Sr(OH)2 > Ca(OH)2 > Mg(OH)2

Explanation:

Ba(OH)2 is the most soluble hydroxide in water because the bond between Ba and OH is the weakest among the given options. Ba(OH)2 is a strong base and a white powder that readily dissolves in water to give a clear, colorless solution. The solubility of Ba(OH)2 in water is about 2.17 g/100 mL of water at room temperature.

Sr(OH)2 is the second most soluble hydroxide among the given options. The bond strength between Sr and OH is stronger than Ba(OH)2 but weaker than Ca(OH)2 and Mg(OH)2. The solubility of Sr(OH)2 in water is about 0.33 g/100 mL of water at room temperature.

Ca(OH)2 is less soluble than Ba(OH)2 and Sr(OH)2 because the bond strength between Ca and OH is stronger than both of them. The solubility of Ca(OH)2 in water is about 0.17 g/100 mL of water at room temperature.

Mg(OH)2 is the least soluble hydroxide among the given options because the bond strength between Mg and OH is the strongest. The solubility of Mg(OH)2 in water is about 0.0096 g/100 mL of water at room temperature.

Hence, the correct option is C) Ba(OH)2.

As we know that down the group the size increases so the bond becomes weaker hence solubility increases down the group...