Which of the following hydrides is capable of showing conformations?

In the staggered conformation of $C_2H_6$,the dihedral angle between $H-C-C-H$ bonds is ....$^o$.

Arrange the following molecules in the correct order of stability (decreasing order):

What is the relationship between the given compounds?

On Pluto,where everything is frozen,astronauts discovered two forms of butane: gauche and anti. Assuming that there are no rotations around single bonds,which statement about the two forms is correct?

The energy difference between the staggered and eclipsed conformations of ethane is