$CuSO_4$ solution reacts with excess $KCN$ to give

The correct order of molar conductivity of the following complex compounds in aqueous solution is:
$(I) K[Co(NH_3)_2(NO_2)_4]$
$(II) [Cr(NH_3)_3(NO_2)_3]$
$(III) [Cr(NH_3)_5NO_2]_3[Co(NO_2)_6]_2$
$(IV) Mg[Cr(NH_3)(NO_2)_5]$

On treatment of $100 \ mL$ of $0.1 \ M$ solution of $CoCl_3 \cdot 6H_2O$ with excess $AgNO_3$,$1.2 \times 10^{22}$ ions are precipitated. The complex is:

The molar ionic conductances of the octahedral complexes are in the order of:
$(1) PtCl_4 \cdot 5NH_3$
$(2) PtCl_4 \cdot 4NH_3$
$(3) PtCl_4 \cdot 3NH_3$
$(4) PtCl_4 \cdot 2NH_3$

The number of hydrogen-bonded water molecule$(s)$ associated with the stoichiometry $CuSO_{4} \cdot 5H_{2}O$ is .... .

The most stable complex among the following is