CBSE 2024 · Region 5 · Set 1 · Q31 · 5 marks
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.
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.
The d-and f-Block ElementsThe LanthanoidsUnderstandlong_answermedium
More from The d-and f-Block Elements
- (i) Silver atom has completely filled d-orbitals in its ground state, it is still considered to be a…2022 · asked 3×
- (i) Describe giving reason which one of the following pairs has the property indicated: (I) Fe or Cu - higher…2026 · asked 3×
- The diamagnetic species is:2025 · asked 3×
- Assertion: Zr and Hf are of almost similar atomic radii. Reason (R): This is due to Lanthanoid contraction.2024 · asked 3×
- (i) When pyrolusite ore is fused with KOH, in presence of air, a dark green coloured product 'A' is obtained…2025 · asked 3×
- The element having [Ar] 3 d^10 4 s^1 electronic configuration is2025 · asked 3×
- From the given E^ values of the first row transition elements, answer the following questions: (i) Why is E…2022 · asked 3×
- Account for the following: (i) Transition metals and their compounds show catalytic activities. (ii) Zn, Cd…2022 · asked 3×
CBSE Class 12 Chemistry past-paper question from the 2024board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.