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Science · 2023 · 2 marks
CBSE 2023 · Region 5 · Set 1 · Q21
On heating 'X' at $\displaystyle 373$ K, it loses water molecules and becomes 'Y'. 'Y' is a substance which doctors use for supporting fractured bones in the right position.(i)Identify 'X' and 'Y'.(ii)How can 'X' be reobtained from 'Y' ?Two solutions M and N give Red and Blue colour respectively with a universal indicator.(i)In which solution will the hydrogen ion concentration be more ? Justify your answer.(ii)If both M and N solutions are mixed and the resultant mixture is tested with a universal indicator, it turns green. What is the nature of the salt formed ? Justify your answer.
On heating 'X' at $\displaystyle 373$ K, it loses water molecules and becomes 'Y'. 'Y' is a substance which doctors use for supporting fractured bones in the right position.
(i)
Identify 'X' and 'Y'.
(ii)
How can 'X' be reobtained from 'Y' ?
Two solutions M and N give Red and Blue colour respectively with a universal indicator.
(i)
In which solution will the hydrogen ion concentration be more ? Justify your answer.
(ii)
If both M and N solutions are mixed and the resultant mixture is tested with a universal indicator, it turns green. What is the nature of the salt formed ? Justify your answer.
Marking-scheme solution
(i)
\(\displaystyle \mathrm{X}=\mathrm{CaSO}_{4} \cdot 2 \mathrm{H}_{2} \mathrm{O}\) /Gypsum / Calcium sulphate dihydrate
\[\mathrm{Y}=\mathrm{CaSO}_{4} \cdot \frac{1}{2} \mathrm{H}_{2} \mathrm{O} / \text { Plaster of Paris/ Calcium sulphate hemi-hydrate }
\]
(ii) \(\displaystyle \mathrm{CaSO}_{4} \cdot \frac{1}{2} \mathrm{H}_{2} \mathrm{O}+1 \frac{1}{2} \mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{CaSO}_{4} \cdot 2 \mathrm{H}_{2} \mathrm{O}\) OR
(b) (i) M, it is an acidic solution
(ii) Neutral M is an acid and N is a base./Neutralization reaction
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CBSE Class 10 Science past-paper question from the 2023board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.