CBSE 2026 · Region 2 · Set 3 · Q24 · 3 marks
(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?
(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
(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.
The d-and f-Block ElementsSome Important Compounds of Transition ElementsApplyshort_answermedium
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CBSE Class 12 Chemistry past-paper question from the 2026board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.