Rotation around carbon-carbon single bond of ethane is not completely free. Justify the statement

Explanation

Rotation about C-C single bond is restricted due to repulsions between the electron clouds of C-H bond on adjacent carbon atoms . As a result of these repulsions , ethane exists in infinite number of conformations out of which two extreme conformations ,i.e., staggered and eclipsed are important .
The staggered conformation is , however , more stable than the eclipsed conformation by about 12.55 kJ `mol^(-1)`. This energy difference of `12.55 kJ mol^(-1)` between the staggered and the eclipsed conformation is , in fact, the energy barrier to rotation about C-C single bond in ethane . However, this energy barrier is not large enough to prevent rotation . Even at room temperature, collisions of the molecules supply sufficient kinetic energy to overcome this energy barrier. Thus, the two conformations are readily interconvertible . As a result , it is not possible to separate the two confomations of ethane. However, at any given moment, most of the molecules would exist in the staggered conformation due to its minimum energy and maximum stability.