Question

g \Which substance has the lowest vapor pressure at 25 °C? Group of answer choices CH3CH2OH CH3CH2CH2OH CH3CH2CH2CH2OH CH3CH2CH2CH2CH2OH

Answer 1

Answer:

CH3CH2CH2CH2CH2OH.

Explanation:

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In this case, since the vapor pressure is known to be the pressure exerted by the gaseous molecules in equilibrium with a liquid, we can infer that the higher the molecule, the lower the vapor pressure because the molecules tend to be help together more strongly and more energy is required to separate them and take them from liquid to gas.

In such a way, since CH3CH2CH2CH2CH2OH is the longest molecule (five carbon atoms) it would be more stable at liquid phase which means that it has less molecules moving to gaseous phase, which is also related with the lowest vapor pressure. Conversely, CH3CH2OH has the highest vapor pressure.

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