Question

unit 3 practice #2
13.
ethyl acetate
butyl acetate
a mixture containing equal numbers of moles of ethyl acetate and butyl acetate was separated using distillation.
based on the diagrams shown above, which of the following identifies the substance that would be initially present
in higher concentration in the distillate and correctly explains why that occurs?
(a) ethyl acetate, because it has fewer c - c bonds to break
(b) ethyl acetate, because it has a shorter carbon chain and weaker london dispersion forces
(c) butyl acetate, because it has more c - c bonds to break
(d) butyl acetate, because it has a longer carbon chain and weaker dipole - dipole attractions

Explanation:

• Intermolecular Forces and Boiling Point: In distillation, substances with lower boiling points vaporize first and are more concentrated in the distillate initially.
• London Dispersion Forces: These are weak intermolecular forces that increase with the length of the carbon chain (more electrons, more surface - area for interaction). Ethyl acetate has a shorter carbon chain compared to butyl acetate. So, ethyl acetate has weaker London dispersion forces.
• Effect on Boiling Point: Weaker intermolecular forces (in this case, weaker London dispersion forces for ethyl acetate) result in a lower boiling point.

Answer:

B. Ethyl acetate, because it has a shorter carbon chain and weaker London dispersion forces