How would you explain ? (i) BeO is insoluble but BeSO_(4) is soluble in water . (ii) BaO is soluble but BaSO_(4) is insoluble in water (iii) LiI is more soluble than KI in ethanol.

How would you explain ? (i) BeO is insoluble but BeSO_(4) is soluble

1.	How would you explain ? (i) BeO is insoluble but BeSO_(4) is soluble in water . (ii) BaO is soluble but BaSO_(4) is insoluble in water (iii) LiI is more soluble than KI in ethanol.
Answer» Solution :(i) Because of smaller SIZE , higher ionization enthalpy and higher electronegativity , BeO is essentially covalent and hence is insoluble in WATER . In contrast , `BeSO_(4)` is ionic . Further because of small size of `Be^(2+)` ion , the hydration energy of `BeSO_(4)` is much higher than its lattice energy and hence `BeSO_(4)` is highly soluble in water . (ii) Both `BaO` and `BaSO_(4)` are ionic compounds . however , the size of `O^(2-)` ion is much smaller than that of the `SO_(4)^(2-)` ion . Since a bigger anion stabilizes a bigger cation more than a smaller anion stabililzes a bigger cation , therefore , the lattice energy of BaO is much smaller than that of `BaSO_(4)` and hence BaO is soluble while `BaSO_(4)` is insoluble in water . (iii) `Li^(+)` is much smaller than `K^(+)` ion . Therefore , according to Fajan RULE , `Li^(+)` ion can polarize bigger `I^(-)` ion to a greater extent than `K^(+)` ion . As a result , LiI is more covalent than KI and hence is more soluble in organic solvents like ethanol.