CBSE 2024 · Region 1 · Set 1 · Q33 · 5 marks

(i)

Account for the following :

(1)

The melting and boiling points of Zn, Cd and Hg are low.

(2)

Of the $\displaystyle \mathrm{d}^{4}$ species, $\displaystyle \mathrm{Cr}^{2+}$ is strongly reducing while $\displaystyle \mathrm{Mn}^{3+}$ is strongly oxidizing.

(3)

$\displaystyle \mathrm{E}^{\mathrm{o}}$ value of $\displaystyle \mathrm{Cu}^{2+} / \mathrm{Cu}$ is $\displaystyle +0 \cdot 34 \mathrm{~V}$.

(ii)

Complete and balance the following chemical equations :

(1)

$\displaystyle \mathrm{KMnO}_{4} \xrightarrow{\text { heat }}$

(2)

$\displaystyle \mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}+6 \mathrm{I}^{-}+14 \mathrm{H}^{+} \longrightarrow$

(i)

Out of $\displaystyle \mathrm{Cu}_{2} \mathrm{Cl}_{2}$ and $\displaystyle \mathrm{CuCl}_{2}$, which is more stable in aqueous solution and why ?

(ii)

Write the general electronic configuration of f-block elements.

(iii)

Predict which of the following will be coloured in aqueous solution and why ? \[\mathrm{Sc}^{3+}, \mathrm{Fe}^{3+}, \mathrm{Zn}^{2+} \] [Atomic number : $\displaystyle \mathrm{Sc}=21, \mathrm{Fe}=26, \mathrm{Zn}=30$ ]

(iv)

How can you obtain potassium dichromate from sodium chromate ?

(v)

Why do transition metals and their compounds show catalytic activities ?

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.