For what eccentricity is the secondary focus (which is usually empty) locatedat the sun? what is the shape of this orbit?

The eccentricity is zero. The shape of the orbit is a circle.

Explanation:

This question is about eccentricity which is calculated by dividing the distance  between the center and focus of the ellipse by the length of the semi-major axis. When the second focus (mostly empty) is situated approximately at the sun, the eccentricity is equivalent to zero. In addition, the shape of this type of orbit is a circle.