which probably has the lowest boiling point at 1.0 atm pressure.

A) C6H14
B) C3H8
C) C4H10
D) C5H12
E) C2H6

i was told that the molecule with the lowest weight has the lowest boiling point because it is the least polar as well.

Partly yes and partly no. The molecule likely to have the lowest boiling point will be the one with the lowest molar mass. The polarity plays a VERY important role but it is another factor to consider; i.e., just because a molecule has a low molar mass doesn't mean it is the least polar.

c2h6

To determine which compound out of C6H14, C3H8, C4H10, C5H12, and C2H6 probably has the lowest boiling point at 1.0 atm pressure, we need to consider the relationship between molecular size and boiling point.

Boiling point is primarily determined by intermolecular forces. The strength of intermolecular forces increases as the molecular size increases. Larger molecules have a greater surface area available for intermolecular interactions, leading to stronger forces and higher boiling points.

Based on this relationship, we can determine that the compound with the smallest molecular size is likely to have the lowest boiling point at 1.0 atm pressure.

Let's compare the molecular sizes of the given compounds:

C6H14 (hexane) - 6 carbon atoms, 14 hydrogen atoms
C3H8 (propane) - 3 carbon atoms, 8 hydrogen atoms
C4H10 (butane) - 4 carbon atoms, 10 hydrogen atoms
C5H12 (pentane) - 5 carbon atoms, 12 hydrogen atoms
C2H6 (ethane) - 2 carbon atoms, 6 hydrogen atoms

From the comparison, we can see that ethane (C2H6) has the smallest molecular size, with just 2 carbon atoms and 6 hydrogen atoms.

Therefore, ethane (C2H6) is expected to have the lowest boiling point at 1.0 atm pressure among the given options.