Which is expected to have the largest dispersion forces? which is expected to have the largest dispersion forces? c12h26 be cl2 c3h8 f2?

The one I would expect to have the largest dispersion forces would be the largest and heaviest molecule. This is evidenced by the fact that that molecule is a liquid at room temperature while all the others are gases.

C3H8 = This is propane and a gas at room temperature

F2 = Also a gas at room temperature

BeCl2 = This is a solid and forms an extended lattice in the form of Be-Cl-Be bridges therefore dispersion forces are not important

Therefore the answer to this is C12H26 which is a wax and a liquid at room temperature.

C12H26