Washing soda () exhibits efflorescence when exposed to dry air. What is the stable product formed as — s Block Elements Chemistry Question

💡 Solution & Explanation

Efflorescence is the spontaneous loss of water of crystallization. When decahydrate washing soda is exposed to air, it loses 9 molecules of water and crumbles to a white powder, forming the monohydrate ($Na_2CO_3 \cdot H_2O$). It only becomes completely anhydrous (soda ash) upon heating above $373\text{ K}$.