How would you explain the following observations? a. BeO is almost insoluble but BeSO_(4) is soluble in water. b. BaO is soluble but BaSO_(4) is insoluble in water. c. Lil is more soluble than Kl in ethanol.

How would you explain the following observations? a. BeO is almost in

1.	How would you explain the following observations? a. BeO is almost insoluble but BeSO_(4) is soluble in water. b. BaO is soluble but BaSO_(4) is insoluble in water. c. Lil is more soluble than Kl in ethanol.
Answer» Solution :a. Because of SMALLER size, higher IONISATION enthalpy and higher electronegativity, `BeO` is essentially covalent and hence is insoluble in water. In constrast,`BaSO_(4)` is ionic. Further because of small size of `Be^(2+)` ion, the hydration enthalpy of `BaSO_(4)` is much higher than is lattice enthalpy and hence `BaSO_(4)` is highly SOLUBLE in water. b. 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 stabilises a bigger cation more than a smaller anion stabilises a bigger cation, THEREFORE, the lattice enthalpy of `BaO` is much smaller than that of `BaSO_(4)` and hence `BaO` is soluble while `BaSO_(4)` is insoluble in water. c. `Li^(o+)` is much smaller than `K^(o+)` ion. Therefore, according to Fajan's rule, `Li^(o+)` ion can polarise bigger `I^(ө)` ion to a greater extent than `K^(o+)` ion. As a result, `Lil` is more covalent that `Kl` and hence is more soluble in organic solvents like ethanol.