Sodium Carbonate is commonly known as ______.

The correct answer is Option (2) → Washing soda

Washing soda is sodium carbonate decahydrate, Na₂CO₃·10H₂O. It is used for washing clothes, for removing the permanent hardness of water and in making glass and soap.

Tip: Baking soda, also called cooking soda, is sodium hydrogen carbonate (NaHCO₃); washing soda is sodium carbonate. The two are often mixed up.