Question

What is the chemical formula of Washing soda?

Answer 1

Hint: Washing soda is the compound of the element of an s-block. It is in a hydrated form which means it has water molecules. On the action of acids, it produces carbon dioxide.

Complete step by step answer:
The chemical formula of washing soda is \[N{{a}_{2}}C{{O}_{3}}.10{{H}_{2}}O\]
Its chemical name is Sodium Carbonate. It is manufactured by the Solvay-ammonia process.
This process is based upon the principle that when carbon dioxide is passed through brine (sodium chloride) solution saturated with ammonia, the following ions are present.
\[N{{a}^{+}},N{{H}_{4}}^{+},C{{l}^{-}} and HC{{O}_{3}}^{-}\]

When carbon dioxide is passed through brine (sodium chloride) solution saturated with ammonia sparingly soluble sodium bicarbonate crystallizes out easily. The crystallized bicarbonate is then calcined to form sodium carbonate.
When carbon dioxide is passed through a brine solution saturated with ammonia, sodium bicarbonate is formed the following reaction take place:
Formation of ammonium and hydroxyl ions:
\[N{{H}_{3}}+{{H}_{2}}O\to N{{H}_{3}}.{{H}_{2}}O\to N{{H}_{4}}^{+}+O{{H}^{-}}\]

Crystallization of bicarbonate ions:
\[N{{a}^{+}}+C{{l}^{-}}+N{{H}_{4}}^{+}+O{{H}^{-}}+C{{O}_{2}}\to N{{a}^{+}}+HC{{O}_{3}}^{-}+N{{H}_{4}}^{+}+C{{l}^{-}}\]

Formation of $NaHC{{O}_{3}}$ as precipitate and ammonium chloride in solution:
\[N{{a}^{+}}+HC{{O}_{3}}^{-}\to NaHC{{O}_{3}}(precipitate)\]
\[N{{H}_{4}}^{+}+C{{l}^{-}}\to N{{H}_{4}}Cl\text{(in solution)}\]

Due to the common ion effect and the presence of\[N{{a}^{+}}\] ions of sodium chloride, sodium bicarbonate precipitates out. It is filtered and then ignited to get sodium carbonate.
\[2NaHC{{O}_{3}}\to N{{a}_{2}}C{{O}_{3}}+C{{O}_{2}}+{{H}_{2}}O\]
The sodium carbonate formed is then purified within its aqueous solution.
By the process of recrystallization from water it forms washing soda, \[N{{a}_{2}}C{{O}_{3}}.10{{H}_{2}}O\].

Properties of washing soda: It is a white crystalline solid as decahydrate (\[N{{a}_{2}}C{{O}_{3}}.10{{H}_{2}}O\])
It is easily soluble in water.

On the action of heat above 373 K, it forms white colored powder called soda ash.
It is a salt of a strong base and weak acid on dissolving it in water, it hydrolysis to form an alkaline solution.
It reacts with mineral acids to evolve carbon dioxide due to the presence of carbonate.
Uses: It is used for the softening of hard water.
It is used in paints.
It is used in the manufacture of soap, borax, etc.

Note: Washing soda is always in the hydrated form. Sometimes in the option sodium carbonate and hydrated form of sodium carbonate could be given, then the correct answer will be a hydrated form of sodium carbonate.