How is washing soda different from sodium bicarbonate ?

Sodium bicarbonate has :

How is sodium carbonate converted into sodium bicarbonate ?

(a). Describe how washing soda is produced starting from sodium chloride (common salt). Write equations of all the reactions involved. (b) State whether an aqueous solution of washing soda is acidic or alkaline? Give reason for your answer. (c) What is meant by saying that washing soda has detergent properties? (d) Give two important uses of washing soda (or sodium carbonate).

When washing soda is heated