Final answer:
Ethanol and ammonia can hydrogen bond to water because they contain hydrogens bound to highly electronegative atoms (oxygen for ethanol and nitrogen for ammonia), with lone pairs available to form hydrogen bonds. Methane and carbon dioxide cannot, as they lack the necessary polar bonds and lone pairs.
Step-by-step explanation:
To answer the question which of the following molecules can hydrogen bond to water, we need to identify which molecules have the capacity for hydrogen bonding. Hydrogen bonds can form when a molecule features a hydrogen atom covalently bound to a highly electronegative atom, such as nitrogen, oxygen, or fluorine, which leads to a polar molecule. This type of bond can occur when these hydrogen atoms are in proximity to lone pairs on electronegative atoms in other molecules.
- Ethanol (CH₃CH₂OH) contains an -OH group with hydrogen directly bonded to oxygen, a highly electronegative atom that has two lone pairs of electrons, making it able to form hydrogen bonds.
- Ammonia (NH₃) has hydrogen atoms bonded to nitrogen, which is another highly electronegative atom with one lone pair of electrons, allowing it to also participate in hydrogen bonding.
- Methane (CH₄) and Carbon dioxide (CO₂) lack hydrogen atoms bonded to highly electronegative atoms and do not have the requisite lone pairs of electrons to act as hydrogen bond donors or acceptors, so they cannot hydrogen bond with water.
Therefore, ethanol and ammonia can form hydrogen bonds with water, while methane and carbon dioxide cannot.