Which of the following compounds has the highest vapor pressure at 25°C?
A. CH3CH2OH
B. CH3OCH3
C. CH3CH2CH2Cl
D. CH3CH2CH3
E. CH3CH2CH2CH
To determine which of the given compounds has the highest vapor pressure at 25°C, we need to consider the intermolecular forces present in each compound. Generally, compounds with weaker intermolecular forces tend to have higher vapor pressures.
Let's examine each compound and the intermolecular forces it exhibits:
A. CH3CH2OH (ethanol) - Ethanol exhibits hydrogen bonding due to the presence of the -OH group.
B. CH3OCH3 (dimethyl ether) - Dimethyl ether does not exhibit hydrogen bonding but has dipole-dipole interactions.
C. CH3CH2CH2Cl (1-chloropropane) - 1-chloropropane exhibits dipole-dipole interactions due to the electronegativity difference between chlorine and carbon.
D. CH3CH2CH3 (propane) - Propane only exhibits London dispersion forces, which are weaker than hydrogen bonding or dipole-dipole interactions.
E. CH3CH2CH2CH (butane) - Butane only exhibits London dispersion forces, similar to propane.
Considering the intermolecular forces present, we can rank the compounds from weakest to strongest forces as follows:
Propane (D) < Butane (E) < 1-chloropropane (C) < Dimethyl ether (B) < Ethanol (A)
Therefore, ethanol (A) with hydrogen bonding has the highest intermolecular forces and consequently the lowest vapor pressure at 25°C. Conversely, propane (D) and butane (E) with only London dispersion forces have the weakest intermolecular forces and the highest vapor pressures at 25°C.
So, the compound with the highest vapor pressure at 25°C among the given options is either propane (D) or butane (E).
To determine which compound has the highest vapor pressure at 25°C, we need to consider the intermolecular forces between the molecules.
Vapor pressure is directly related to the strength of the intermolecular forces - the weaker the forces, the higher the vapor pressure.
Let's analyze the choices:
A. CH3CH2OH (ethyl alcohol) has hydrogen bonding, which is a strong intermolecular force. Hydrogen bonding leads to lower vapor pressure compared to other compounds without hydrogen bonding.
B. CH3OCH3 (dimethyl ether) does not have hydrogen bonding. Instead, it has London dispersion forces, which are relatively weaker compared to hydrogen bonding.
C. CH3CH2CH2Cl (1-chloropropane) has dipole-dipole interactions due to the presence of a polar C-Cl bond. These forces are stronger than London dispersion forces but weaker than hydrogen bonding.
D. CH3CH2CH3 (propane) does not have any polar bonds or functional groups. It only has London dispersion forces, which are the weakest intermolecular forces.
E. CH3CH2CH2CH3 (butane) does not have any polar bonds or functional groups. It only has London dispersion forces, which are the weakest intermolecular forces.
Based on the analysis, compound B (CH3OCH3) has the weakest intermolecular forces (London dispersion forces) among the given choices. Therefore, it will have the highest vapor pressure at 25°C.
So, the compound with the highest vapor pressure at 25°C is CH3OCH3 (choice B).