go to UNSW home page
UNSW logo School of Chemistry Home Page
> Contacts   > Sitemap
About the School divider Research divider Graduate Study divider Undergraduate Study divider High School Resources

Intermolecular Forces

Review - 4

Which of the following substances contain molecules attracted to each other by hydrogen bonds?

(a) CH4 (methane)
(b) C2H5OH (ethanol or ethyl alcohol)
(c) NH3 (ammonia)
(d) CH3-O-CH3 (dimethyl ether)

Hints

Remember the requirements for hydrogen bonds to form: the molecule must contain a hydrogen atom directly bonded to a nitrogen, oxygen or fluorine atom and there must be one of these atoms (N, O, or F) for the hydrogen to bond to.

Answers

(a) Methane contains hydrogen atoms, but not N, or O or F. Therefore there cannot be hydrogen bonds between methane molecules.

(b) Ethanol does contain a hydrogen atom bonded to an oxygen atom. Thus there can be hydrogen bonds formed between the hydrogen in the OH group on one ethanol molecule and the oxygen atom in the OH group on another ethanol molecule.

(c) Ammonia does contain a hydrogen atom bonded to a nitrogen atom. Thus there can be hydrogen bonds formed between the hydrogen atoms in one ammonia molecule and the nitrogen atom in another ammonia molecule.

(d) Dimethyl ether does contain an oxygen atom and several hydrogen atoms, but the hydrogens are not directly bonded to the oxygen. This means that the hydrogen atoms do not carry a large enough partial positive charge to take part in hydrogen bonding.

 

< Review - 3 Review - 5 >