Question

How is NaHCO3 converted into washing soda

Answer 1

Sodium hydrogen carbonate dehydrates when it is heated, forming sodium carbonate. The CO2 can be recycled to produce more NaHCO3 by the Solvay process. Sodium carbonate is also called soda ash and washing soda. Sodium carbonate is used in laundry detergents as a softening agent.

Answer 2

sodium carbonate  or washing soda can be obtained by heating baking soda , recrystallisation of sodium carbonate gives washing soda 
tht is 
                          
                     Na2CO3 + 10H​2O GIVES  Na2CO3.10H2O