Which of the following molecules could form hydrogen bonds with an identical molecule?

• A. CH_4
• B. CO_2
• C. NH_3
• D. C_2H_6

Answer: (C)

Verified step by step guidance

1. Understand what hydrogen bonding is: it is a special type of dipole-dipole interaction that occurs when a hydrogen atom is covalently bonded to a highly electronegative atom such as nitrogen (N), oxygen (O), or fluorine (F), and this hydrogen interacts with a lone pair of electrons on another electronegative atom in a nearby molecule.
2. Examine each molecule to see if it contains hydrogen atoms bonded to N, O, or F, and if the molecule has lone pairs on these atoms to accept hydrogen bonds.
3. For CH_4 (methane), note that hydrogen is bonded to carbon, which is not electronegative enough to create hydrogen bonding, so CH_4 cannot form hydrogen bonds with itself.
4. For CO_2 (carbon dioxide), there are no hydrogen atoms at all, so it cannot form hydrogen bonds with itself.
5. For NH_3 (ammonia), hydrogen atoms are bonded to nitrogen, which is electronegative and has lone pairs, so NH_3 molecules can form hydrogen bonds with each other.