When an aqueous solution of borax is acidified with hydrochloric acid, a white crystalline solid is formed which is soapy to touch. Is this solid acidic or basic in nature? Explain.


Orthoboric acid is formed when the aqueous solution is acidified with borax. Orthoboric acid is crystalline and soapy to touch. It is soluble in hot water.

Na2B4O7 + 2HCl + 5H2O 2NaCl + 4B(OH)3


Boric acid is a weak monobasic acid. It acts a lewis acid by taking electrons from the hydroxyl group.


B(OH)3 + 2H2O [B[OH]4]- + H3O+


Heating orthoboric acid at 370K gives metaboric acid and on further heating give Boric acid


H3BO3 HBO2 B2O3


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