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Science · 2025 · 3 marks
CBSE 2025 · Region 5 · Set 1 · Q27
Write chemical formula of washing soda. How is it obtained from baking soda? List two uses of washing soda.
Write chemical formula of washing soda. How is it obtained from baking soda ? List two uses of washing soda.
Marking-scheme solution
\(\displaystyle \mathrm{Na}_{2} \mathrm{CO}_{3} .10 \mathrm{H}_{2} \mathrm{O}\)
When baking soda is heated sodium carbonate is obtained and recrystallisation of sodium carbonate gives washing soda. /
\[\begin{aligned}
& 2 \mathrm{NaHCO}_{3} \xrightarrow{\text { heat }} \mathrm{Na}_{2} \mathrm{CO}_{3}+\mathrm{H}_{2} \mathrm{O}+\mathrm{CO}_{2} \\
& \mathrm{Na}_{2} \mathrm{CO}_{3}+10 \mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{Na}_{2} \mathrm{CO}_{3} .10 \mathrm{H}_{2} \mathrm{O}
\end{aligned}
\]
Uses:(i) In glass / soap / paper industry
(ii) In manufacture of borax
(iii) As cleansing agent for domestic purpose
(iv) Removing permanent hardness of water
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