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Science · 2025 · 2 marks
CBSE 2025 · Region 5 · Set 1 · Q21
A crystalline substance of green colour 'X' emits gases of characteristic odour when heated over a flame. It first loses water and changes colour. On…
A crystalline substance of green colour 'X' emits gases of characteristic odour when heated over a flame. It first loses water and changes colour. On further heating, it decomposes and produces a solid compound Y.
(a)
Identify 'X' and 'Y'.
(b)
State the change in colour observed when 'X' is heated.
Marking-scheme solution
(a) \(\displaystyle \mathrm{X}=\mathrm{FeSO}_{4} \cdot 7 \mathrm{H}_{2} \mathrm{O} /\) Ferrous Sulphate Crystals
\(\displaystyle \mathrm{Y}=\mathrm{Fe}_{2} \mathrm{O}_{3} /\) Ferric Oxide
(b) Green to white /brown
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CBSE Class 10 Science past-paper question from the 2025 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.