CBSE 2025 · Region 5 · Set 1 · Q27 · 3 marks
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
Acids, Bases and SaltsChemicals from Common SaltUnderstandshort_answereasy
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CBSE Class 10 Science past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.