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Science · 2026 · 1 mark
CBSE 2026 · Region 2 · Set 1 · Q17
Which of the following are combination reactions ?(i)$\displaystyle 2 \mathrm{KClO}_{3} \longrightarrow 2 \mathrm{KCl}+3 \mathrm{O}_{2}$(ii)$\displaystyle \mathrm{MgO}+\mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{Mg}(\mathrm{OH})_{2}$(iii)$\displaystyle 4 \mathrm{Al}+3 \mathrm{O}_{2} \longrightarrow 2 \mathrm{Al}_{2} \mathrm{O}_{3}$(iv)$\displaystyle \mathrm{Zn}+\mathrm{FeSO}_{4} \longrightarrow \mathrm{ZnSO}_{4}+\mathrm{Fe}$
Which of the following are combination reactions ?
(i)
$\displaystyle 2 \mathrm{KClO}_{3} \longrightarrow 2 \mathrm{KCl}+3 \mathrm{O}_{2}$
(ii)
$\displaystyle \mathrm{MgO}+\mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{Mg}(\mathrm{OH})_{2}$
(iii)
$\displaystyle 4 \mathrm{Al}+3 \mathrm{O}_{2} \longrightarrow 2 \mathrm{Al}_{2} \mathrm{O}_{3}$
(iv)
$\displaystyle \mathrm{Zn}+\mathrm{FeSO}_{4} \longrightarrow \mathrm{ZnSO}_{4}+\mathrm{Fe}$
Official answer
From CBSE’s own marking scheme for this paper.
(D)
(ii) and (iii)
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CBSE Class 10 Science past-paper question from the 2026board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.