CBSE 2023 · Region 5 · Set 2 · Q35 · 5 marks
(a)A transition element X has electronic configuration [Ar] $\displaystyle 4 \mathrm{~s}^{2} 3 \mathrm{~d}^{3}$. Predict its likely oxidation states. $\displaystyle \mathbf{1}+\mathbf{1}+\mathbf{3}=\mathbf{5}$(b)Complete the reaction mentioning all the products formed : $\displaystyle 2 \mathrm{KMnO}_{4} \xrightarrow{\Delta}$(c)Account for the following :(i)In the 3d transition series, zinc has the lowest enthalpy of atomisation.(ii)$\displaystyle \mathrm{Cu}^{+}$ion is unstable in aqueous solution.(iii)Actinoids show more number of oxidation states than lanthanoids.
(a)
A transition element X has electronic configuration [Ar] $\displaystyle 4 \mathrm{~s}^{2} 3 \mathrm{~d}^{3}$. Predict its likely oxidation states. $\displaystyle \mathbf{1}+\mathbf{1}+\mathbf{3}=\mathbf{5}$
(b)
Complete the reaction mentioning all the products formed : $\displaystyle 2 \mathrm{KMnO}_{4} \xrightarrow{\Delta}$
(c)
Account for the following :
(i)
In the 3d transition series, zinc has the lowest enthalpy of atomisation.
(ii)
$\displaystyle \mathrm{Cu}^{+}$ion is unstable in aqueous solution.
(iii)
Actinoids show more number of oxidation states than lanthanoids.
Marking-scheme solution
(a)
+$\displaystyle 2$, +$\displaystyle 3$, +$\displaystyle 4$, +$\displaystyle 5$
(b)
\(\displaystyle 2 \mathrm{KMnO}_{4} \xrightarrow{\Delta} \mathrm{~K}_{2} \mathrm{MnO}_{4}+\mathrm{MnO}_{2}+\mathrm{O}_{2}\)
(i)
It has \(\displaystyle \mathrm{d}^{10}\) configuration / absence of unpaired electrons in d-orbitals resulting in weak metallic bonding.
The d-and f-Block ElementsGeneral Properties of the Transition Elements (d-Block)Applylong_answermedium
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CBSE Class 12 Chemistry past-paper question from the 2023board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.