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MCAT Chemistry Question — Hydrogen Bonds

  • by John
  • May 13, 2018
  • MCAT Question of the Day

In comparison with 1,2-dihydroxyethane, ethanol has weaker intermolecular hydrogen bonds resulting in:

 

A. a lower boiling point for ethanol due to weaker intermolecular forces.

B. ethanol being a stronger base.

C. a higher boiling point because ethanol is a higher molecular weight compound than 1,2-dihydroxyethane.

D. weaker intramolecular bonds in ethanol due to overall reduced bonding energy.

Click for Explanation

Ethane-1,2-diol (ethylene glycol) has one more hydroxyl group than ethanol, resulting in greater intermolecular hydrogen bonding. Due to the higher intermolecular forces, ethane-1,2-diol has a boiling point of 200°C in comparison with 78°C for ethanol.

A. a lower boiling point for ethanol due to weaker intermolecular forces. Correct.

B. ethanol being a stronger base. Incorrect, The two hydroxyl groups on ethylene glycol confer greater basicity than the one hydroxyl group of ethanol.

C. a higher boiling point because ethanol is a higher molecular weight compound than ethane-1,2-diol. Incorrect, ethanol is a lower molecular weight compound than ethylene glycol.

D. weaker intramolecular bonds in ethanol due to overall reduced bonding energy. Incorrect, Bond energy does not decrease because of intermolecular hydrogen bonding.

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