Choose the substance with the highest vapor pressure at a given temperature.
A) SiS2 B) RbCl C) CH3SCH3 D) BF3 E) SbH3

The answer is d but I don't know why my guess was c because it is a smaller molecule which means less London/dispersion forces.

Question

Choose the substance with the highest vapor pressure at a given temperature.
 A) SiS2              B) RbCl   C) CH3SCH3  D) BF3              E) SbH3

The answer is d but I don't know why my guess was  c because it is a smaller molecule which means less London/dispersion  forces.

mww · Answer

@meleigha 
BF3 is actually non-polar even though an individual B-F bond is highly polarised. It is a special case of electron deficient valence shell (thus it does not obey the 'octet' rule).

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The overall structure is trigonal planar with sp2 hybridisation, notice there is no net dipole moment.

mww · Answer

I will also specify it is often incorrectly said that dispersion forces are linked with increasing size of atom. Although there is some degree of correlation, more precisely, it is linked with increasing total numbers of electrons.