Which of the following compounds is expected to have the HIGHEST boiling point (

Question

Which of the following compounds is expected to have the HIGHEST boiling point (bpt? CH_3OCH_3 CH_3CH_2OH CH_3CH_2CH_2CH_3 CH_3CH_2CH_3 CH_3Cl CH_3OCH_3 This molecule displays dipole-dipole because the oxygen is much CH_3OCH_2CH_3 CH_3OCH_3 CH_3CH_2OH CH_3CH_2CH_2CH_3 CH_3CH_3CH_2Cl. Which of the following compounds is expected to have the HIGHEST vapor pressure? CH_3CH_2CH_3 CH_3OCH_3 CH_3CH_2OH CH_3CH_2CH_2CH_3 CH_3CH_2CH_2Cl The vapor pressure of a liquid increases with an increase in temperature. Which of the following statements best explains this increase? The average kinetic energy of molecules is greater;thus more molecules can enter the gaseous state. The number of gaseous molecules above the liquid remains constant, but these molecules have greater average kinetic energy. The faster-moving molecules in the liquid exert a greater pressure. All the molecules have greater kinetic energies. The intermolecular forces between the molecules decrease at higher temperatures Which of the following substances is most likely to exist as a gas at 25 degree C and l atm pressure? CaO C_8H_18 SbCl_3 LiCl B_2H_6 Neon atoms do not combine to form Ne_2 molecules, yet neon atoms can be liquefied through the following intermolecular forces: dipole-dipole ion-dipole dipole-induced dipole dispersion nonmetal-nonmetal

Explanation / Answer

1. The boiling point of the given compounds are as follows:

a. CH3OCH3 = -24OC (dimethyl ether)

b. CH3CH2OH= 78.37OC (ethanol)

c. CH3CH2CH2CH3 = -1 to 1 OC (butane)

d. CH3CH2CH3 = -42OC (propane)

e. CH3Cl = 61.2OC (chloroform)

Also dimethyl ether, butane and propane exists as gas at room temperature and atmospheric pressure.

DImethyl ether exhibit dipole-dipole interaction, butane exhibit Van der Waals forces and propane exhibit van der Waals dispersion forces which are weaker than those of ethanol.

therefore, they have lower boiling point.

Chloroform and ethanol are in liquid state at room temperature and atmospheric pressure. Ethanol exhibit dipole-dipole, hydrogen bonding, and London dispersion forces. But the intermolecular forces in ethanol is stronger than chlorform.

Hence, ethanol ( the option "b") has the highest boiling point.

2. Lower the boiling point, higher is the vapour pressure.

since, propane is having lowest boiling point and it exist as gas it has highest vapour pressure.

The correct answer is a. CH3CH2CH3 .

3. The vapour pressure of liquid increases with an increase in temperature because the average kinetic energy of the molecules is greater; thus more molecules enter the gaseous state.

As the temperature of a liquid rises, so does its vapor pressure.

According to Kinetic Molecular Theory, the average energy of molecules increases as the temperature increases. The vapor pressure above the surface of the liquid will increase.

therefore the correct option is "a".

4. CaO, SbCl3 and LiCl are ionic compounds. So they exists as solids. Gaseous ionic compounds are not known.

C8H18 is an non polar hydrocarbon and exhinbit London dispersion forces. Since it is a larger molecule and contains more electrons it is more polarizable. The octane boils at a higher temperature because of its greater polarizability. It exists as liquid at room temperature.

The correct option is e. B2H6

5. Neon atoms do not combine to form Ne2 molecules, yet neon atoms can be liquified through dispersion forces.

This is the only attraction experienced by noble gas atoms.

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