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

The two structures $I$ and $II$ represent:

Given below are two statements:
Statement $I$: There are several conformers for $n$-butane. Out of those conformers,the fully eclipsed conformer (dihedral angle $0^{\circ}$) is the least stable and the anti-staggered conformer (dihedral angle $180^{\circ}$) is the most stable.
Statement $II$: As the dihedral angle increases from $0^{\circ}$ to $60^{\circ}$,torsional strain decreases from the fully eclipsed conformer $(X)$ to the gauche conformer $(Y)$.
In the light of the above statements,choose the correct answer from the options given below:

What do you mean by dihedral angle or torsional angle?

Give the difference between eclipsed ethane and staggered ethane.

What will be the stability order in case of ethylene glycol?