CBSE 2025 · Region 1 · Set 1 · Q25 · 3 marks
The elements of 3d transition series are given as : Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn Answer the following :(a)Copper has exceptionally positive $\displaystyle \mathrm{E}_{\mathrm{M}^{2+} / \mathrm{M}}^{\circ}$ value, why ?(b)Which element is a strong reducing agent in +$\displaystyle 2$ oxidation state and why ?(c)$\displaystyle \mathrm{Zn}^{2+}$ salts are colourless. Why ?
The elements of 3d transition series are given as : Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn Answer the following :
(a)
Copper has exceptionally positive $\displaystyle \mathrm{E}_{\mathrm{M}^{2+} / \mathrm{M}}^{\circ}$ value, why ?
(b)
Which element is a strong reducing agent in +$\displaystyle 2$ oxidation state and why ?
(c)
$\displaystyle \mathrm{Zn}^{2+}$ salts are colourless. Why ?
Marking-scheme solution
(a)
Its high
and low
(b)
Cr
Cr3+ (d4 to d3) / stable half-filled t2g level
(c)
Fully-filled d-orbitals hence no d-d transition / due to the absence of unpaired electron.
The d-and f-Block ElementsGeneral Properties of the Transition Elements (d-Block)Understandshort_answermedium
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CBSE Class 12 Chemistry past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.