Question

Account for the following: 

(a) A solution of Na₂CO₃ is alkaline. 

(b) Ba(OH)₂ is soluble in water while Baso₄ is almost insoluble.

Answer 1

(a) Na₂CO₃ + H₂O ⇌ H₂CO₃ + 2 NaOH 

or CO₃²⁻ + 2 Na⁺ + 2H₂O ⇌ 2Na⁺ +2OH⁻ + H₂CO₂ 

Or CO₃²⁻ + 2H₂O ⇌ H₂CO₃ + 2OH⁻ 

Since N₂CO₃ produces OH⁻ ions in solution, hence N₂CO₃ solution is alkaline is nature. 

(b) The lattice enthalpy of BaSO₄ is much more than its hydration enthalpy and hence it is insoluble in water. But hydration enthalpy of Ba(OH)₂ is much more than lattice enthalpy. Therefore, Ba(OH)₂ is soluble in water.