CBSE 2024 · Region 4 · Set 1 · Q31 · 5 marks
Attempt any five of the following :(a)Why Zinc is not regarded as a transition element ?(b)What is Lanthanoid contraction ?(c)Why is first ionization enthalpy of chromium lower than that of Zn ?(d)Why are transition elements good catalysts ?(e)Compounds of transition metals are generally coloured. Give reason.(f)Out of $\displaystyle \mathrm{KMnO}_{4}$ and $\displaystyle \mathrm{K}_{2} \mathrm{MnO}_{4}$, which one is paramagnetic and why ?(g)Complete the following ionic equation : \[\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}+14 \mathrm{H}^{+}+6 \mathrm{e}^{-} \longrightarrow \] $\displaystyle \mathbf{1} \boldsymbol{\times} \mathbf{5}$
Attempt any five of the following :
(a)
Why Zinc is not regarded as a transition element ?
(b)
What is Lanthanoid contraction ?
(c)
Why is first ionization enthalpy of chromium lower than that of Zn ?
(d)
Why are transition elements good catalysts ?
(e)
Compounds of transition metals are generally coloured. Give reason.
(f)
Out of $\displaystyle \mathrm{KMnO}_{4}$ and $\displaystyle \mathrm{K}_{2} \mathrm{MnO}_{4}$, which one is paramagnetic and why ?
(g)
Complete the following ionic equation : \[\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}+14 \mathrm{H}^{+}+6 \mathrm{e}^{-} \longrightarrow \] $\displaystyle \mathbf{1} \boldsymbol{\times} \mathbf{5}$
Marking-scheme solution
(a) Zn hasfully filled d-orbital configuration in ground state and in its oxidized state.
(b) The filling of 4f orbital before 5d orbital results in steady decrease in atomic radii and ionic radii. / The steady decrease in the atomic radii or ionic radii of the elements with increase in atomic number.
(c) In chromium an electron is removed from \(\displaystyle 4 s^{1}\) while in Zn it is from fully filled \(\displaystyle 4 s^{2}\) orbital.
(d) Due to variable oxidation stateandcomplex formation /provide large surface area.
(e) Due to d-d transition of electrons in d- orbitals / unpaired electrons in d-orbital.
(f) \(\displaystyle \mathrm{K}_{2} \mathrm{MnO}_{4}\), due to the presence of one unpaired electron.
(g) \(\displaystyle \mathrm{Cr}_{2} \mathrm{O}_{7}{ }^{2-}+14 \mathrm{H}^{+}+6 \mathrm{e}^{-} \longrightarrow 2 \mathrm{Cr}^{3+}+7 \mathrm{H}_{2} \mathrm{O}\)
The d-and f-Block ElementsElectronic Configurations of the d-Block ElementsUnderstandlong_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.