Number of water molecules in washing soda and soda ash respectively are:

We need to find the number of water molecules in washing soda and soda ash respectively.

Washing soda: Washing soda is the common name for hydrated sodium carbonate. Its chemical formula is $$Na_2CO_3 \cdot 10H_2O$$ (sodium carbonate decahydrate). The "deca" prefix indicates 10 water molecules. Washing soda is obtained by recrystallizing soda ash from aqueous solution, and the crystals that form contain 10 molecules of water of crystallization per formula unit. Therefore, washing soda has 10 water molecules.

Soda ash: Soda ash is the common name for anhydrous sodium carbonate, $$Na_2CO_3$$. The term "ash" comes from its historical production by burning plant material and extracting the residue. Being anhydrous, soda ash contains 0 (zero) water molecules. It is essentially the same compound as washing soda but without the water of crystallization.

Key distinction: Both washing soda and soda ash are forms of sodium carbonate ($$Na_2CO_3$$). The difference is that washing soda is the hydrated form ($$Na_2CO_3 \cdot 10H_2O$$) while soda ash is the anhydrous form ($$Na_2CO_3$$). When washing soda is heated, it loses its water of crystallization and becomes soda ash.

The correct answer is Option 3: 10 and 0.