Question

which of the following should have the lowest boiling point? give an explanation

A.) CH3OH

B.) H2S

C.) NH3

D.) HCl

E.) CH4

Answer 1

CH4 would have the lowest boiling point.

Just look at these compounds' intermolecular forces. Out of these four compounds MeoH can form one hydrogen bond per molecule because it has one acidic protan. has the strongest, because it is very polar and has two polar hydrogens per molecule, so that each oxygen atom essentially has two covalent bonds and two hydrogen bonds.

Remaining three compounds NH3, H2S and CH4, Which molecule has the higher attractive forces, CH4 or NH3 or H2S?

Since Methane is a small, nonpolar, hydrocarbon, the only attractive force its molecules have london forces.
Ammonia and H2S on the other hand not only experiences london forces, but also have one of the most attractive forces...Hydrogen bonding.
For this reason, Ammonia and H2S gases will have a higher boiling point than methane.