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Chemistry · 2024 · 5 marks
CBSE 2024 · Region 5 · Set 1 · Q31
Attempt any five of the following: 1 × 5 (a) Ce(III) is easily oxidised to Ce(IV). Comment. (b) E^°( Mn^2+ / Mn ) is -1.18 V. Why is this value…
Attempt any five of the following : $\displaystyle \mathbf{1} \boldsymbol{\times} \mathbf{5}$
(a)
Ce(III) is easily oxidised to Ce(IV). Comment.
(b)
$\displaystyle \mathrm{E}^{\circ}\left(\mathrm{Mn}^{2+} / \mathrm{Mn}\right)$ is -$\displaystyle 1.18$ V. Why is this value highly negative in comparison to neighbouring d block elements ?
(c)
Which element of 3d series has lowest enthalpy of atomisation and why ?
(d)
What happens when sodium chromate is acidified ?
(e)
Zn, Cd and Hg are soft metals. Why ?
(f)
Why is permanganate titration not carried out in the presence of HCl ?
(g)
The lower oxides of transition metals are basic whereas the highest are amphoteric/acidic. Give reason.
Marking-scheme solution
(a)
Ce (IV) ion has more stable configuration \(\displaystyle \left(4 \mathrm{f}^{0}\right)\) than \(\displaystyle \mathrm{Ce}(\mathrm{III})\) ion.
(b)
Due to extra stability of half filled \(\displaystyle \left(\mathrm{d}^{5}\right)\) orbitals in \(\displaystyle \mathrm{Mn}^{2+}\)
(c)
Zinc, due to completely filled d-orbitals/ weak metallic bonding.
(d)
It gets converted to sodium dichromate/colour changes fromyellow to orange/ correct equation.
(e)
Due to completely filled d-orbitals/ weak metallic bonding
(f)
HCl is oxidized by \(\displaystyle \mathrm{KMnO}_{4}\) to \(\displaystyle \mathrm{Cl}_{2}\).
(g)
Lower oxides of transition metals are ionic& ionic character decreases orcovalent character increasewith increase in oxidation state.
All The d-and f-Block Elements questions2024 question paperNCERT solutions: The d-and f-Block ElementsPractice The d-and f-Block Elements →
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CBSE Class 12 Chemistry past-paper question from the 2024 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.