304.
$$C{u^ + }$$ ion is not stable in aqueous solution because
A
second ionisation enthalpy of copper is less than the first ionisation enthalpy
B
large value of second ionisation enthalpy of copper is compensated by much more negative hydration energy of $$Cu_{\left( {aq} \right)}^{2 + }$$
C
hydration energy of $$Cu_{\left( {aq} \right)}^{ + }$$ is much more negative than that of $$Cu_{\left( {aq} \right)}^{2 + }$$
D
many copper $$\left( I \right)$$ compounds are unstable in aqueous solution and undergo disproportionation reaction
Answer :
large value of second ionisation enthalpy of copper is compensated by much more negative hydration energy of $$Cu_{\left( {aq} \right)}^{2 + }$$
All the four metals have nearly the same metallic radii and hence nearly the same atomic volume. On account of higher atomic mass of copper it has high density amongst given metals.
307.
Which of the following dissolve in hot conc.$$NaOH$$ solution
Among these alloys, only steel contains carbon which is a non-metal.
309.
$$CuS{O_4}$$ when reacts with $$KCN$$ forms $$CuCN$$ which is insoluble in water. It is soluble in excess of $$KCN$$ due to the formation of the complex
A
$${K_2}\left[ {Cu{{\left( {CN} \right)}_4}} \right]$$
B
$${K_3}\left[ {Cu{{\left( {CN} \right)}_4}} \right]$$
C
$$Cu{\left( {CN} \right)_2}$$
D
$$Cu\left[ {KCu{{\left( {CN} \right)}_4}} \right]$$
$$CuS{O_4}$$ reacts with $$KCN$$ to give a white precipitate of cuprous cyanide and cyanogen gas. The cuprous cyanide dissolves in excess of $$KCN$$ forming $${K_3}\left[ {Cu{{\left( {CN} \right)}_4}} \right].$$
$$\eqalign{
& CuS{O_4} + 2KCN \to {K_2}S{O_4} + \mathop {Cu{{\left( {CN} \right)}_2}}\limits_{{\text{Unstable}}} \cr
& 2Cu{\left( {CN} \right)_2} \to \mathop {2CuCN}\limits_{{\text{Insoluble}}} + \mathop {CN - CN}\limits_{{\text{cyanogen}}} \cr
& CuCN + 3KCN \to \mathop {{K_3}\left[ {Cu{{\left( {CN} \right)}_4}} \right]}\limits_{{\text{Soluble}}} \cr} $$
310.
In the following reactions, $$ZnO$$ is respectively acting as a/an:
$$\eqalign{
& \left( A \right)\,\,ZnO + N{a_2}O \to N{a_2}Zn{O_2} \cr
& \left( B \right)\,\,ZnO + C{O_2} \to ZnC{O_3} \cr} $$
Although $$ZnO$$ is an amphoteric oxide but in given reaction.
$$\eqalign{
& \left( A \right)\,\mathop {ZnO}\limits_{acid} + \mathop {N{a_2}O}\limits_{base} \to \mathop {N{a_2}Zn{O_2}}\limits_{salt} \cr
& \left( B \right)\,\mathop {ZnO}\limits_{base} + \mathop {C{O_2}}\limits_{acid} \to \mathop {ZnC{O_3}}\limits_{salt} \cr} $$