Of the ions ${\mathrm{Co}}^{2+},{\mathrm{Sc}}^{3+}$ and ${\mathrm{Cr}}^{3+}$ which one will give coloured aqueous solutions and how will each of them respond to a  magnetic field and why ? 

$\text{ (Atomic numbers: }\mathrm{Co},=27,\mathrm{Sc}=21,\mathrm{Cr}=24)$

Represent the reaction of acidified ${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7$ with 

$\text{ (i) }\mathrm{KI}$  solution 

Represent the reaction of acidified ${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7$ with 

${\mathrm{FeSO}}_4$

 Represent the reaction of acidified ${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7$ with 

${\mathrm{H}}_2 \mathrm{S}$ with the help of chemical equations.