Assertion (A) Separation of Zr and Hf is difficult.
Reason (R) Because Zr and Hf lie in the same group of the Periodic Table.
Assertion (A) Actinoids form relatively less stable complexes as compared to lanthanoids.
Reason (R) Actinoids can utilise their $5 f$ orbitals alongwith 6d orbitals in bonding but lanthanoids do not use their 4 f orbital for bonding.
Assertion (A) Cu cannot liberate hydrogen from acids.
Reason (R) Because it has positive electrode potential.
Assertion (A) The highest oxidation state of osmium is +8 .
Reason (R) Osmium is a 5 d -block element.
Identify A to E and also explain the reaction involved.
The substances from $A$ to $E$ are
$$A=\mathrm{Cu} ; B=\mathrm{Cu}\left(\mathrm{NO}_3\right)_2 ; C=\left[\mathrm{Cu}\left(\mathrm{NH}_3\right)_4\right]^{2+} ; D=\mathrm{CO}_2 ; E=\mathrm{CaCO}_3$$
(i) $\mathrm{CuCO}_3 \xrightarrow{\Delta} \mathrm{CuO}+\mathrm{CO}_2] \times 2$
(ii) $2 \mathrm{CuO}+\mathrm{CuS} \longrightarrow \underset{[A]}{3 \mathrm{Cu}}+\mathrm{SO}_2$
(iii) $\underset{[A]}{\mathrm{Cu}}+4 \mathrm{HNO}_3$ (conc.) $\longrightarrow \underset{[B]}{\mathrm{Cu}\left(\mathrm{NO}_3\right)_2}+2 \mathrm{NO}+2 \mathrm{H}_2 \mathrm{O}$
(iv) $\underset{[B]}{\mathrm{Cu}^{2+}}+\mathrm{NH}_3 \longrightarrow \underset{\substack{\text { [C] (Blue solution)}}}{\left[\mathrm{Cu}\left(\mathrm{NH}_3\right)_4\right]}$
(v) $$Ca{(OH)_2} + \mathop {C{O_2}}\limits_{[D]} \buildrel {} \over \longrightarrow \mathop {CaC{O_3}}\limits_{[E]\,(Milky)} + {H_2}O$$
(vi) $\mathrm{CaCO}_3+\mathrm{H}_2 \mathrm{O}+\mathrm{CO}_2 \longrightarrow \mathrm{Ca}\left(\mathrm{HCO}_3\right)_2$