Chemical formula of washing soda is:
a.) \[N{a_2}C{O_3}\]
b.) \[N{a_2}C{O_3}.10{H_2}O\]
c.) \[N{a_2}C{O_3}.5{H_2}O\]
d.) \[N{a_2}S{O_4}.10{H_2}O\]

Answer Verified Verified
Hint: Try to recall that washing soda is a white crystalline solid which exists as decahydrate and on heating, the decahydrate loses the water of crystallisation and changes to a white powder called soda ash. Now by using this you can easily find the correct option from the given options.

Complete step by step solution:
-It is known to you that washing soda is a white crystalline solid which exists as a decahydrate and is readily soluble in water.
-It reacts with dilute mineral acids evolving carbon dioxide.
-Also, it gets hydrolysed by water to form an alkaline solution.
-On strong heating, it loses all its water of crystallisation and becomes completely anhydrous and changes to white powder called soda ash.
-Now, since it is known to you that \[N{a_2}C{O_3}\] is soda ash. So, you can easily say that \[N{a_2}C{O_3}.10{H_2}O\] is the chemical formula of washing as it is the hydrated form of soda ash.
Therefore, from above we can say that option B is the correct option for the given question.

Additional information:
The important uses of washing powder are as follows:
-It is used for softening of hard water.
-It is used for washing purposes in laundry.
-Also, it is used as a reagent in the laboratory.
-It is used for the manufacture of soap, glass, paper, borax, caustic soda etc.
-It is used for metal refining.

Note: -It should be remembered that sodium carbonate is generally prepared commercially by Solvay process or ammonia soda process.
-Also, you should remember that washing soda is also used in the textile and petroleum industry.
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