Hydrogen Bonding

Question

Of these substances in the pure liquid phase which one exhibits hydrogen bonding?

a) CHF3

b)CH3-O-CH3

c)H2SO4

d)all of these

I'm not sure why its only H2SO4

Answer 1

Linda had a great explanation of hydrogen bonding! I'll add that many students misinterpret where the hydrogen bond/intermolecular force is located. Remember, when it comes to hydrogen bonding, we are talking about INTERmolecular forces (London Dispersion Forces, Dipole-Dipole, Ion-Dipole, and Hydrogen Bondign), not INTRAmolecular forces (ionic, covalent, metallic bonds). The hydrogen bond exists between a Hydrogen atom that is covalently bonded to a very electronegative atom (F, O, or N) and a lone pair on a nearby very electronegative atom (F, O, or N). For example, in water (H₂O) many students think that the hydrogen bond exists between the O and the H that are covalently bonded together in the same molecule. However, the hydrogen bond exists between a lone pair on the Oxygen atom and a hydrogen atom on a nearby water molecule.

 

I'll follow this description up with a question that demonstrates the definition of hydrogen bonding - Which has stronger intermolecular forces, liquid water (H₂O) or ammonia (NH₃)?

Answer 2

Hydrogen bonding occurs in polar molecules when hydrogen has a partially positive charge from being bound to a highly electronegative atom (O, F, or N). Only in the sulfuric acid is the hydrogen bound to an electronegative atom.