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Chemistry · 2026 · 3 marks
CBSE 2026 · Region 2 · Set 3 · Q24
(a) Complete and balance the following equations: (i) 2 Na_2 CrO_4+2 H^+ → (ii) 5 S^2-+2 MnO_4^-+16 H^+ → (b) Why is chemistry of actinoids…
(a)
Complete and balance the following equations : \[\text { (i) } \quad 2 \mathrm{Na}_{2} \mathrm{CrO}_{4}+2 \mathrm{H}^{+} \longrightarrow \]
(ii)
$\displaystyle 5 \mathrm{~S}^{2-}+2 \mathrm{MnO}_{4}{ }^{-}+16 \mathrm{H}^{+} \longrightarrow$
(b)
Why is chemistry of actinoids complicated as compared to lanthanoids?
Marking-scheme solution
(a)(i)
$\displaystyle 2$ Na2CrO4 + 2H+ → Na2Cr2O7 + 2Na+ + H2O
(ii)
5S2− + 2MnO4− + 16H+ → 2Mn2+ + 8H2O + 5S
(b)
Because of their radioactive nature and their existence in wide range of
oxidation states.
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CBSE Class 12 Chemistry past-paper question from the 2026 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.