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Science · 2026 · 2 marks
CBSE 2026 · Region 4 · Set 1 · Q25
(a) A compound 'A' is used in soda-lime fire-extinguisher and decomposes on heating to form compound 'B'. Compound 'B' is used for removing permanent…
(a)
A compound 'A' is used in soda-lime fire-extinguisher and decomposes on heating to form compound 'B'. Compound 'B' is used for removing permanent hardness of water. Identify 'A' and 'B'.
(b)
Write chemical formula of Plaster of Paris. At what temperature gypsum is heated to obtain Plaster of Paris ?
Marking-scheme solution
(a)
A → Sodium hydrogen carbonate/ baking soda/ \(\displaystyle \mathrm{NaHCO}_{3}\)
B → Sodium carbonate/ washing soda/ \(\displaystyle \mathrm{Na}_{2} \mathrm{CO}_{3}\)
(b) \(\displaystyle \cdot \mathrm{CaSO}_{4} \cdot \frac{1}{2} \mathrm{H}_{2} \mathrm{O}\)
\(\displaystyle 373 \mathrm{~K} / 100^{\circ} \mathrm{C}\)
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CBSE Class 10 Science past-paper question from the 2026 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.