achieve week 5 hw question 12

[505766240]

If a solid line represents a covalent bond and a dotted line represents intermolecular attraction, which of the choices shows a hydrogen bond?

H3N⋅⋅⋅⋅⋅⋅H−O−H

H−H

H4C⋅⋅⋅⋅⋅⋅H−F

H2O⋅⋅⋅⋅⋅⋅H−CH3

[ashna kumar 3k]

For this question, the answer that I came to was the interaction that is shown in the first diagram. A hydrogen bond has to be shown by the dotted line, and between two molecules; thus the H-H cannot be the answer. H4C⋅⋅⋅⋅⋅⋅H−F is not the answer because in H4C, the electrons are shared very equally and thus none of the atoms carry a partial positive or negative charge to form a hydrogen bond. H3N⋅⋅⋅⋅⋅⋅H−O−H is the best answer because H2O definitely is polar with partially negative oxygen and partially positive and in H3N, N is a highly electronegative atom that has a lone pair which would make it partially negative, allowing the hydrogen bond to form.

[KatieWu 1E]

You can tell that it's a hydrogen bond because one side has a highly electronegative atom with a lone pair of N, O, or F, and in this case it is N. The other side consists of a hydrogen atom bonded to a highly electronegative atom. So, H3N....H-O-H shows a hydrogen bond

[Aneesha_Nema_3C]

Hydrogen bonds are intermolecular forces so H - H doesn't work because that's just a covalent bond. In order for a hydrogen bond to occur, the hydrogen atom has to be directly bonded to a highly electronegative atom, so H2O⋅⋅⋅⋅⋅⋅H−CH3 wouldn't work because the hydrogen is bonded to a carbon, which isn't electronegative enough. The hydrogen bond itself needs to be between hydrogen and a highly electronegative atom, so H4C⋅⋅⋅⋅⋅⋅H−F wouldn't work. Because of this, only H3N⋅⋅⋅⋅⋅⋅H−O−H would be a valid answer.