\( q = 0, \, \Delta T = 0, \, w = 0 \)
\( q = 0, \, \Delta T<0, \, w \neq 0 \)

During free expansion of an ideal gas under adiabatic conditions, there is no transfer of heat, no work is done, and the temperature remains constant.
The compound with molecular formula C\(_6\)H\(_6\), which gives only one monobromo derivative and takes up four moles of hydrogen per mole for complete hydrogenation has ___ \(\pi\) electrons.