Question

Which two statements about propene and ethanol are true? Н Н Н, Н—С —С—ОН Н H Н Н ethanol propene Ethanol has a lower vapor pressure than propene at a given temperature. and ethanol have London forces and dipole-dipole forces. Both propene Propene has a higher boiling point than ethanol due to its double bond Ethanol forms hydrogen bonds, whereas propene has dipole-dipole interactions Of the two compounds, only ethanol forms hydrogen bonds. о

Answer 1

London dispersion forces are present in propene. In ethanol, in addition to London dispersion forces, weak van der Waals forces are present. The boiling point of ethanol is higher than the boiling point of propene due to intermolecular hydrogen bonding in ethanol. Hydrogen bonds are present in ethanol whereas, in propene, London dispersion forces (weak van der Waals forces) are present. Propene being nonpolar lacks dipole-dipole forces. Hence, the statements "Both propene and ethanol have London forces and dipole-dipole forces", "Propene has a higher boiling point than ethanol due to its double bond", and "Ethanol forms hydrogen bonds, whereas propene has dipole-dipole interactions" are the incorrect statements. A hydrogen bond is formed when H atom is attached to electronegative N, O or F atom. Hence, alcohol, amines, and hydrofluoric acid show hydrogen bond formation whereas hydrocarbons do not show hydrogen bond formation. In ethanol. H atom is attached to electronegative O atom of hydroxyl group. Hence, ethanol forms hydrogen bonds. In propene. H atom is attached to C atom which is NOT an electronegative N. O or F atom. Hence, propene cannot form hydrogen bonds. Due to the formation of hydrogen bonds, the molecules of ethanol associates. This lowers vapor pressure and raises boiling point. No such molecular association is present in propene. Hence, ethanol has lower vapor pressure and higher boiling point than propene. Hence, the following two statements are correct: "Ethanol has a lower vapor pressure than propene at a given temperature". "Of the two compounds, only ethanol forms hydrogen bonds".