Predict the order of increasing vapor pressure at a given temperature for the following compounds:
CH3CH2CH2CH2OH
HOCH2CH2CH2OH
CH3CH2OCH2CH3
Vapor pressure is another way of saying decreasing boiling point. Lower molar masses mean lower boiling points. More hydrogen bonding means higher boiling points.
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HOCH2CH2CH2OH
To predict the order of increasing vapor pressure for the given compounds, we need to understand the factors that affect vapor pressure.
Vapor pressure is the pressure exerted by the vapor of a liquid in a closed system at equilibrium. It is influenced by intermolecular forces, specifically the strength of the forces holding the molecules together. The weaker the intermolecular forces, the higher the vapor pressure.
One factor that affects intermolecular forces is the molecular size. Larger molecules tend to have stronger intermolecular forces due to increased surface area for bonding, which leads to lower vapor pressure.
With that in mind, let's analyze the given compounds:
1. CH3CH2CH2CH2OH (butanol):
This compound has a longer carbon chain compared to the other two. Longer carbon chains mean larger molecular size, which results in stronger intermolecular forces. Therefore, it will have the lowest vapor pressure.
2. HOCH2CH2CH2OH (propan-1-ol):
This compound has one less carbon compared to butanol. The removal of one carbon decreases the molecular size, which results in weaker intermolecular forces compared to butanol. Thus, it will have a higher vapor pressure than butanol.
3. CH3CH2OCH2CH3 (diethyl ether):
This compound has the smallest molecular size among the three. The presence of oxygen and the absence of hydroxyl group make the intermolecular forces weaker compared to both butanol and propan-1-ol. Consequently, it will have the highest vapor pressure among the three compounds.
So, the predicted order of increasing vapor pressure at a given temperature is:
CH3CH2CH2CH2OH < HOCH2CH2CH2OH < CH3CH2OCH2CH3