All AP Chemistry Resources
Example Questions
Example Question #1 : Intermolecular Forces
Put the following in order from greatest to least intermolecular forces:
I. H2O
II. LiOH
III. CO2
II>III>I
I>III>II
I>II>III
II>I>III
III>I>II
II>I>III
LiOH displays ion-dipole IMF, H2O displays hydrogen bonding, and CO2 displays dipole-dipole. Ion-dipole is greater than hydrogen bonding as an IMf, and hydrogen bonding is greater than dipole-dipole.
Example Question #2 : Intermolecular Forces
Put the following intermolecular forces in order of decreasing strength:
London dispersion forces; hydrogen bonds; dipole-dipole interactions; ion-dipole interactions
Hydrogen bonds
ion-dipole interactions
dipole-dipole interactions
London dispersion forces
Dipole-dipole interactions
Hydrogen bonds
Ion-dipole interactions
London dispersion forces
ion-dipole interactions
hydrogen bonds
dipole-dipole interactions
London dispersion forces
Hydrogen bonds
dipole-dipole interactions
London dispersion forces
Ion-dipole interactions
ion-dipole interactions
hydrogen bonds
dipole-dipole interactions
London dispersion forces
Ion-dipole forces are the forces responsible for the solvation of ionic compounds in aqueous solutions, and are the strongest of the intermolecular foces. Hydrogen bonding is the second strongest intermolecular force, followed by dipole-dipole interactions. London dispersion forces are present in all solutions, but are very small and the weakest of the intermolecular forces.
Example Question #13 : Compounds And Molecules
Which of the following intermolecular forces account for the fact that noble gases can liquefy?
Ion dipole interactions
Hydrogen bonding
Dispersion forces
Dipole dipole interactions
Dispersion forces
Noble gases are uncharged and do not have polar covalent bonds or dipole moments. The only force that could apply to them are dispersion forces.
Example Question #1 : Bonding And Forces
Which of the following is most similar to hydrogen bonding?
The slightly negatively charged sulfur atoms in are attracted to the slightly positively charged hydrogen atom of a nearby molecule.
The chlorine bound to carbon in dichloromethane will slightly attract positive charged particles.
Water completely dissolves certain salts, like .
Two methane molecules are attracted to one another because of temporary dipoles.
A negatively charged chlorine anion in solution will attract nearby positively charged Lithium cations.
The slightly negatively charged sulfur atoms in are attracted to the slightly positively charged hydrogen atom of a nearby molecule.
The choice "The slightly negatively charged sulfur atoms in are attracted to the slightly positively charged hydrogen atom of a nearby molecule" is exactly analogous to hydrogen bonding in water.
"Two methane molecules are attracted to one another because of temporary dipoles" describes London dispersion forces.
While "A negatively charged chlorine anion in solution will attract nearby positively charged Lithium cations" may sound like hydrogen bonding, it is more descriptive of interactions between any charged particles, not charged particles within the same molecule.
"Water completely dissolves certain salts, like " does not describe bonding at all.
While "The chlorine bound to carbon in dichloromethane will slightly attract positive charged particles" sounds promising, the slight charges are not on the same molecule.
Example Question #3 : Intermolecular Forces
Methanol (H3COH) exhibits all of the following intermolecular forces EXCEPT __________.
London dispersion forces
Hydrogen bonding
Ionic bonding
Dipole-dipole interactions
Ionic bonding
Methanol is not an ionic molecule and will not exhibit intermolecular ionic bonding.
Methanol is polar, and will exhibit dipole interactions. It also contains the -OH alcohol group which will allow for hydrogen bonding.
Example Question #15 : Compounds And Molecules
Which of the following intermolecular forces creates the strongest relative attraction?
Hydrogen bonding
Dispersion forces
Dipole-ion interactions
Dipole-dipole interactions
Dipole-ion interactions
Dipole-ion interactions (an attraction between an ion and a neutral, but polar atom) are the strongest intermolecular forces listed. Ion-ion forces (attraction between two ions) are the strongest interactions overall.
Hydrogen bonding, an attraction between a hydrogen atom and a highly electronegative atom like fluorine, oxygen, or nitrogen, is the second strongest interaction listed.
The third strongest listed is dipole-dipole interactions, an attraction between two polar molecules, followed by dispersion forces, temporary shifts in the electrons of a molecule.
Example Question #4 : Intermolecular Forces
Which intermolecular force is responsible for the high surface tension of water?
Hydrogen bonding
Dispersion forces
Covalent bonding
Van der Waals forces
Hydrogen bonding
Hydrogen bonding is what holds the hydrogen in one molecule of water to the oxygen in another molecule. Surface tension is a measure of the difficulty to disturb the surface of a liquid. The strong intermolecular connections created by hydrogen bonding makes it hard to disrupt adjacent molecules and break the water surface.
Most key properties of water are attributed to its hydrogen bonding.
Example Question #11 : Intermolecular Forces
What intermolecular forces can be found in a molecule of ethene?
London dispersion forces only
London dispersion forces, hydrogen bonding, and dipole-dipole attraction
Dipole-dipole attraction and ionic bonding
London dispersion forces and dipole-dipole attraction
London dispersion forces and hydrogen bonding
London dispersion forces only
Ethene is an organic molecule composed of two carbon atoms, joined by a double bond, and four hydrogen atoms.
Ethene, like all molecules, exhibits London dispersion forces. This molecule, however, has no net dipole moment, so it will not exhibit dipole-dipole attraction. Also, even though it contains hydrogens, it does not exhibit hydrogen bonding. To exhibit hydrogen bonding, the hydrogen atoms must be attached to more electronegative atoms, namely nitrogen, fluorine, or oxygen. Finally, ionic bonding is only present in ionic compounds, not organic compounds.
Example Question #12 : Intermolecular Forces
Which of the following has the highest boiling point?
Ionic bonds are the strongest type of bonds, followed by covalent bonds, hydrogen bonds, and lastly, van Der waals forces.
Example Question #13 : Intermolecular Forces
Which of the following substances has a higher boiling point?
Dipropyl Ether
Propanol
They have equal boiling points
Dipropyl ether
You must know the system temperature in order to determine the answer
You must know the system pressure in order to determine the answer
Propanol
Propanol
Although the two molecules seem similar in structure, proponol has a higher boiling point due to the hydrogen bonding allowed by its alcohol group. This creates a strong intermolecular force, and extra energy is subsequently needed to break these bonds, resulting in a higher boiling point.
System pressure and temperature are related to boiling point, but are not necessary when comparing the properties of two molecules.