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Science · 2024 · 3 marks
CBSE 2024 · Region 1 · Set 1 · Q27
Write one chemical equation each for the chemical reaction in which the following have taken place :(i)Change in colour(ii)Change in temperature(iii)Formation of precipitate Mention colour change/temperature change (rise/fall)/compound precipitated along with equation.
Write one chemical equation each for the chemical reaction in which the following have taken place :
(i)
Change in colour
(ii)
Change in temperature
(iii)
Formation of precipitate Mention colour change/temperature change (rise/fall)/compound precipitated along with equation.
Marking-scheme solution
(i) Change in colour: The solution will become green in colour.
\[\mathrm{Fe}(\mathrm{~s})+\mathrm{CuSO}_{4}(\mathrm{aq}) \rightarrow \mathrm{FeSO}_{4}+\mathrm{Cu}(\mathrm{~s})
\]
Blue Green
(ii) Change in temperature: The temperature will increase.
\(\displaystyle \mathrm{NaOH}(\mathrm{aq})+\mathrm{HCl}(\mathrm{aq}) \rightarrow \mathrm{NaCl}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{O}(\mathrm{l})+\) Heat
(iii) Formation of precipitate: Yellow precipitate of \(\displaystyle \mathrm{PbI}_{2}\) is formed.
\[\mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2}(\mathrm{aq})+2 \mathrm{KI}(\mathrm{aq}) \rightarrow \underset{\text { Yellow }}{\mathrm{PbI}_{2}(\mathrm{~s})}+2 \mathrm{KNO}_{3}(\mathrm{aq})
\]
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CBSE Class 10 Science past-paper question from the 2024board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.