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MCAT Chemistry Question — Hydrogen Bonds

  • by John
  • Sep 10, 2014
  • MCAT Question of the Day

Hydrogen bonds form between H2O molecules, but not H2S, H2Se, or H2Te. This explains why:

 

a) H2O is liquid at room temperature while the other compounds are gases.

b) H2O is more volatile than the other compounds.

c) H2O has the highest molecular weight of all four compounds.

d) H2O has a more distinct aroma than the other compounds.

 

Explanation

Hydrogen bonds between H2O molecules will keep the molecules closer together than molecules lacking hydrogen bonds. Choice A is the best choice.

a) H2O is liquid at room temperature while the other compounds are gases, correct.

b) H2O is more volatile than the other compounds, incorrect, Hydrogen bonding will make the H2O less volatile than compounds that do not similarly hydrogen bond.

c) H2O has the highest molecular weight of all four compounds, incorrect, Molecular weight has nothing to do with hydrogen bonds.

d) H2O has a more distinct aroma than the other compounds, incorrect, Molecular aromas result from some functional groups and conjugated pi systems; aromas do not result from hydrogen bonding. Water is also odorless.

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