Question

Why are sodium carbonate and sodium bicarbonate considered basic?

Answer 1

When we look into the preparation of NaHCO3. For better understanding i am writing reaction

NaOH + H2CO3 NaHCO3 + H2O

In aqueous solution, the anion undergoes hydrolysis to give free OH^- ions and the acid, H2CO3 :
HCO3^- + H2O = H2CO3 + OH^-

In above reaction , NaOH is stong base that we know and H2CO3 (carbonic acid) is weak acid. NaHCO3 (Sodium bicarbonate salt fomed from strong base NaOH and weak acid (H2CO3).

After hydrolysis of bicarbonate ions, OH^-ions remains in the solution thats why NaHCO3 considered as a basic.

When Sodium carbonate dissolves in water then then 2 moles of OH^- forms . Reaction is under below

Na₂CO₃ + H₂O 2 Na⁺ + 2 OH^- + H₂CO₃

Since 2 moles of OH^-ions foms afer the hydrolysis of Na₂CO₃

_{Since H2CO3 is a weak electrolyte so H+ will not be found. The concentration of OH- ions is high compared to H+ . So the solution will be basic.}