Final answer:
The sawhorse projection of the ethane molecule shows the staggered conformation, which is more stable due to reduced torsional strain compared to the eclipsed conformation.
Step-by-step explanation:
The sawhorse projection of the ethane molecule is a way to visualize the spatial arrangement of the atoms in the molecule. In the sawhorse projection, one views the C-C bond from an oblique angle, showing the spatial orientation of the hydrogen atoms around the two carbon atoms. To represent the staggered conformation of ethane in a sawhorse projection, the hydrogen atoms attached to the front carbon are drawn angled one way, while those attached to the rear carbon are drawn angled opposite to those on the front carbon. This creates a staggered arrangement that minimizes the repulsion between the hydrogen atoms.
The staggered conformation of ethane is the more stable form compared to the eclipsed conformation. This is because, in the staggered conformation, the hydrogen atoms on one carbon are positioned at the maximum distance possible from the hydrogen atoms on the adjacent carbon, which reduces the torsional strain. The eclipsed conformation has a higher energy level by 12.5 kJ/mol due to the increased torsional strain from the hydrogens being directly in line with each other.