Answer: Be2+ has high charge density and large hydration enthalpy that overcomes the lattice energy; Ba2+ is large with lower hydration enthalpy.
- A Be2+ has high charge density and large hydration enthalpy that overcomes the lattice energy; Ba2+ is large with lower hydration enthalpy
- B BeSO4 generally happens to possess a much lower overall lattice energy than BaSO4 does in the crystal as widely reported in standard practice
- C BaSO4 supposedly carries a noticeably greater degree of ionic character than the corresponding beryllium salt under most conditions encountered
- D Ba2+ is actually claimed to be a far more strongly polarising cation than the small, dense Be2+ ion as frequently observed in practice
Correct answer: A. Be2+ has high charge density and large hydration enthalpy that overcomes the lattice energy; Ba2+ is large with lower hydration enthalpy
Explanation: For Group 2 sulfates: solubility decreases down the group (Be > Mg > Ca > Sr > Ba) because hydration enthalpy decreases faster than lattice energy as cation size increases.
Each s-block metal ion emits a characteristic flame colour because heating excites electrons to higher energy levels; light is emitted as they fall back, with the colour determined by the specific energy gap.
Concept context
Group 1 (alkali metals) and Group 2 (alkaline earth metals). Learn their reactions with water and air, important compounds like NaOH, Na₂CO₃, and CaCO₃, and anomalous behaviour of lithium and beryllium.