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Chemistry · 2025 · 2 marks
CBSE 2025 · Region 2 · Set 3 · Q19
Complete and balance the following chemical equations: 2 × 1 (a) 8 MnO_4^-+3 S_2 O_3^2-+ H_2 O → (b) Cr_2 O_7^2-+3 Sn^2++14 H^+ →
Complete and balance the following chemical equations : $\displaystyle \mathbf{2} \boldsymbol{\times} \mathbf{1}$
(a)
$\displaystyle 8 \mathrm{MnO}_{4}^{-}+3 \mathrm{~S}_{2} \mathrm{O}_{3}^{2-}+\mathrm{H}_{2} \mathrm{O} \longrightarrow$
(b)
$\displaystyle \mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}+3 \mathrm{Sn}^{2+}+14 \mathrm{H}^{+} \longrightarrow$
Marking-scheme solution
(a)
$\displaystyle 8\mathrm{MnO}_4^{-} + 3\mathrm{S}_2\mathrm{O}_3^{2-} + \mathrm{H}_2\mathrm{O} \longrightarrow 8\mathrm{MnO}_2 + 6\mathrm{SO}_4^{2-} + 2\mathrm{OH}^{-}$
(b)
$\displaystyle \mathrm{Cr}_2\mathrm{O}_7^{2-} + 3\mathrm{Sn}^{2+} + 14\mathrm{H}^{+} \rightarrow 2\mathrm{Cr}^{3+} + 3\mathrm{Sn}^{4+} + 7\mathrm{H}_2\mathrm{O}$
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CBSE Class 12 Chemistry past-paper question from the 2025 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.