Question
Sulphates of $$Be$$ and $$Mg$$ are readily soluble in water but sulphates of $$Ca, Sr$$ and $$Ba$$ are insoluble. This is due to the fact
A.
the greater hydration enthalpies of $$B{e^{2 + }}$$ and $$M{g^{2 + }}$$ overcome the lattice enthalpy
B.
high lattice enthalpy of $$B{e^{2 + }}$$ and $$M{g^{2 + }}$$ makes them soluble in water
C.
solubility decreases from $$BeS{O_4}$$ to $$BaS{O_4}$$ due to increase in ionic size
D.
$$BeS{O_4}$$ and $$MgS{O_4}$$ are ionic in nature while other sulphates are covalent
Answer :
the greater hydration enthalpies of $$B{e^{2 + }}$$ and $$M{g^{2 + }}$$ overcome the lattice enthalpy
Solution :
Due to smaller size their lattice enthalpies are high but their greater hydration enthalpies overcome the lattice enthalpies and they become soluble in water. $$Ca, Sr$$ and $$Ba$$ sulphates are insoluble is water due to lower hydration enthalpies.