Which alkane isomer of $C_8H_{18}$ gives only two monochloroalkanes upon reaction with $Cl_2$ in the presence of UV light?

The compound formed when silver powder is heated with chloroform:

The reaction, ${\rm{C}}{{\rm{H}}_3}{\rm{Br}} + {\rm{Na}} o product$, is called

The reaction, ${\rm{C}}{{\rm{H}}_3}{\rm{Br}} + {\rm{Na}} o product$, is called

${{\rm{C}}_2}{{\rm{H}}_5}{\rm{I}} + {{\rm{C}}_5}{{\rm{H}}_{11}}{\rm{I}} + 2{\rm{Na}}\xrightarrow{{Ether}}{{\rm{C}}_2}{{\rm{H}}_5}-{{\rm{C}}_5}{{\rm{H}}_{11}} + 2{\rm{Nal}}$

The above equation represents: